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permissions  rwrr 
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(* Title: HOL/Ring_and_Field.thy 
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ID: $Id$ 
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Author: Gertrud Bauer, Steven Obua, Tobias Nipkow, Lawrence C Paulson, and Markus Wenzel, 
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with contributions by Jeremy Avigad 
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*) 
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14738  7 
header {* (Ordered) Rings and Fields *} 
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15229  9 
theory Ring_and_Field 
15140  10 
imports OrderedGroup 
15131  11 
begin 
14504  12 

14738  13 
text {* 
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The theory of partially ordered rings is taken from the books: 

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\begin{itemize} 

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\item \emph{Lattice Theory} by Garret Birkhoff, American Mathematical Society 1979 

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\item \emph{Partially Ordered Algebraic Systems}, Pergamon Press 1963 

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\end{itemize} 

19 
Most of the used notions can also be looked up in 

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\begin{itemize} 

14770  21 
\item \url{http://www.mathworld.com} by Eric Weisstein et. al. 
14738  22 
\item \emph{Algebra I} by van der Waerden, Springer. 
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\end{itemize} 

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*} 

14504  25 

22390  26 
class semiring = ab_semigroup_add + semigroup_mult + 
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assumes left_distrib: "(a \<^loc>+ b) \<^loc>* c = a \<^loc>* c \<^loc>+ b \<^loc>* c" 

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assumes right_distrib: "a \<^loc>* (b \<^loc>+ c) = a \<^loc>* b \<^loc>+ a \<^loc>* c" 

14504  29 

22390  30 
class mult_zero = times + zero + 
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assumes mult_zero_left [simp]: "\<^loc>0 \<^loc>* a = \<^loc>0" 

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assumes mult_zero_right [simp]: "a \<^loc>* \<^loc>0 = \<^loc>0" 

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22390  34 
class semiring_0 = semiring + comm_monoid_add + mult_zero 
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22390  36 
class semiring_0_cancel = semiring + comm_monoid_add + cancel_ab_semigroup_add 
14504  37 

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instance semiring_0_cancel \<subseteq> semiring_0 
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proof 
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fix a :: 'a 
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have "0 * a + 0 * a = 0 * a + 0" 
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by (simp add: left_distrib [symmetric]) 
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thus "0 * a = 0" 
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by (simp only: add_left_cancel) 
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have "a * 0 + a * 0 = a * 0 + 0" 
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by (simp add: right_distrib [symmetric]) 
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thus "a * 0 = 0" 
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by (simp only: add_left_cancel) 
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qed 
14940  51 

22390  52 
class comm_semiring = ab_semigroup_add + ab_semigroup_mult + 
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assumes distrib: "(a \<^loc>+ b) \<^loc>* c = a \<^loc>* c \<^loc>+ b \<^loc>* c" 

14504  54 

14738  55 
instance comm_semiring \<subseteq> semiring 
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proof 

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fix a b c :: 'a 

58 
show "(a + b) * c = a * c + b * c" by (simp add: distrib) 

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have "a * (b + c) = (b + c) * a" by (simp add: mult_ac) 

60 
also have "... = b * a + c * a" by (simp only: distrib) 

61 
also have "... = a * b + a * c" by (simp add: mult_ac) 

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finally show "a * (b + c) = a * b + a * c" by blast 

14504  63 
qed 
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22390  65 
class comm_semiring_0 = comm_semiring + comm_monoid_add + mult_zero 
14504  66 

14738  67 
instance comm_semiring_0 \<subseteq> semiring_0 .. 
14504  68 

22390  69 
class comm_semiring_0_cancel = comm_semiring + comm_monoid_add + cancel_ab_semigroup_add 
14940  70 

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instance comm_semiring_0_cancel \<subseteq> semiring_0_cancel .. 

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instance comm_semiring_0_cancel \<subseteq> comm_semiring_0 .. 
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22390  75 
class zero_neq_one = zero + one + 
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assumes zero_neq_one [simp]: "\<^loc>0 \<noteq> \<^loc>1" 

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22390  78 
class semiring_1 = zero_neq_one + semiring_0 + monoid_mult 
14504  79 

22390  80 
class comm_semiring_1 = zero_neq_one + comm_semiring_0 + comm_monoid_mult 
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(*previously almost_semiring*) 

14738  82 

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instance comm_semiring_1 \<subseteq> semiring_1 .. 

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class no_zero_divisors = zero + times + 
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assumes no_zero_divisors: "a \<noteq> \<^loc>0 \<Longrightarrow> b \<noteq> \<^loc>0 \<Longrightarrow> a \<^loc>* b \<noteq> \<^loc>0" 

14504  87 

22390  88 
class semiring_1_cancel = semiring + comm_monoid_add + zero_neq_one 
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+ cancel_ab_semigroup_add + monoid_mult 

14940  90 

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instance semiring_1_cancel \<subseteq> semiring_0_cancel .. 

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instance semiring_1_cancel \<subseteq> semiring_1 .. 
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22390  95 
class comm_semiring_1_cancel = comm_semiring + comm_monoid_add + comm_monoid_mult 
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+ zero_neq_one + cancel_ab_semigroup_add 

14738  97 

14940  98 
instance comm_semiring_1_cancel \<subseteq> semiring_1_cancel .. 
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instance comm_semiring_1_cancel \<subseteq> comm_semiring_0_cancel .. 

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instance comm_semiring_1_cancel \<subseteq> comm_semiring_1 .. 
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22390  104 
class ring = semiring + ab_group_add 
14738  105 

14940  106 
instance ring \<subseteq> semiring_0_cancel .. 
14504  107 

22390  108 
class comm_ring = comm_semiring + ab_group_add 
14738  109 

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instance comm_ring \<subseteq> ring .. 

14504  111 

14940  112 
instance comm_ring \<subseteq> comm_semiring_0_cancel .. 
14738  113 

22390  114 
class ring_1 = ring + zero_neq_one + monoid_mult 
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14940  116 
instance ring_1 \<subseteq> semiring_1_cancel .. 
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22390  118 
class comm_ring_1 = comm_ring + zero_neq_one + comm_monoid_mult 
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(*previously ring*) 

14738  120 

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instance comm_ring_1 \<subseteq> ring_1 .. 

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14738  123 
instance comm_ring_1 \<subseteq> comm_semiring_1_cancel .. 
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class ring_no_zero_divisors = ring + no_zero_divisors 
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class ring_1_no_zero_divisors = ring_1 + ring_no_zero_divisors 
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22390  129 
class idom = comm_ring_1 + no_zero_divisors 
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instance idom \<subseteq> ring_1_no_zero_divisors .. 
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22390  133 
class division_ring = ring_1 + inverse + 
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assumes left_inverse [simp]: "a \<noteq> \<^loc>0 \<Longrightarrow> inverse a \<^loc>* a = \<^loc>1" 

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assumes right_inverse [simp]: "a \<noteq> \<^loc>0 \<Longrightarrow> a \<^loc>* inverse a = \<^loc>1" 

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instance division_ring \<subseteq> ring_1_no_zero_divisors 
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proof 
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fix a b :: 'a 
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assume a: "a \<noteq> 0" and b: "b \<noteq> 0" 
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show "a * b \<noteq> 0" 
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proof 
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assume ab: "a * b = 0" 
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hence "0 = inverse a * (a * b) * inverse b" 
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by simp 
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also have "\<dots> = (inverse a * a) * (b * inverse b)" 
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by (simp only: mult_assoc) 
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also have "\<dots> = 1" 
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using a b by simp 
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finally show False 
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by simp 
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qed 
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qed 
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class field = comm_ring_1 + inverse + 
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assumes field_inverse: "a \<noteq> 0 \<Longrightarrow> inverse a \<^loc>* a = \<^loc>1" 
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assumes divide_inverse: "a \<^loc>/ b = a \<^loc>* inverse b" 
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instance field \<subseteq> division_ring 
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proof 
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fix a :: 'a 
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assume "a \<noteq> 0" 
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thus "inverse a * a = 1" by (rule field_inverse) 
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thus "a * inverse a = 1" by (simp only: mult_commute) 
14738  165 
qed 
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instance field \<subseteq> idom .. 
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22390  169 
class division_by_zero = zero + inverse + 
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assumes inverse_zero [simp]: "inverse \<^loc>0 = \<^loc>0" 

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23389  172 

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subsection {* Distribution rules *} 
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text{*For the @{text combine_numerals} simproc*} 
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lemma combine_common_factor: 
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"a*e + (b*e + c) = (a+b)*e + (c::'a::semiring)" 
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by (simp add: left_distrib add_ac) 
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lemma minus_mult_left: " (a * b) = (a) * (b::'a::ring)" 
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apply (rule equals_zero_I) 
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apply (simp add: left_distrib [symmetric]) 
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done 
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lemma minus_mult_right: " (a * b) = a * (b::'a::ring)" 
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apply (rule equals_zero_I) 
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apply (simp add: right_distrib [symmetric]) 
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done 
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lemma minus_mult_minus [simp]: "( a) * ( b) = a * (b::'a::ring)" 
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by (simp add: minus_mult_left [symmetric] minus_mult_right [symmetric]) 
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lemma minus_mult_commute: "( a) * b = a * ( b::'a::ring)" 
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by (simp add: minus_mult_left [symmetric] minus_mult_right [symmetric]) 
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lemma right_diff_distrib: "a * (b  c) = a * b  a * (c::'a::ring)" 
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by (simp add: right_distrib diff_minus 
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minus_mult_left [symmetric] minus_mult_right [symmetric]) 
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lemma left_diff_distrib: "(a  b) * c = a * c  b * (c::'a::ring)" 
14738  201 
by (simp add: left_distrib diff_minus 
202 
minus_mult_left [symmetric] minus_mult_right [symmetric]) 

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203 

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204 
lemmas ring_distribs = 
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205 
right_distrib left_distrib left_diff_distrib right_diff_distrib 
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206 

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text{*This list of rewrites simplifies ring terms by multiplying 
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208 
everything out and bringing sums and products into a canonical form 
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209 
(by ordered rewriting). As a result it decides ring equalities but 
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210 
also helps with inequalities. *} 
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211 
lemmas ring_simps = group_simps ring_distribs 
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212 

22390  213 
class mult_mono = times + zero + ord + 
214 
assumes mult_left_mono: "a \<sqsubseteq> b \<Longrightarrow> \<^loc>0 \<sqsubseteq> c \<Longrightarrow> c \<^loc>* a \<sqsubseteq> c \<^loc>* b" 

215 
assumes mult_right_mono: "a \<sqsubseteq> b \<Longrightarrow> \<^loc>0 \<sqsubseteq> c \<Longrightarrow> a \<^loc>* c \<sqsubseteq> b \<^loc>* c" 

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22390  217 
class pordered_semiring = mult_mono + semiring_0 + pordered_ab_semigroup_add 
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218 

22390  219 
class pordered_cancel_semiring = mult_mono + pordered_ab_semigroup_add 
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220 
+ semiring + comm_monoid_add + cancel_ab_semigroup_add 
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221 

14940  222 
instance pordered_cancel_semiring \<subseteq> semiring_0_cancel .. 
223 

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instance pordered_cancel_semiring \<subseteq> pordered_semiring .. 
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225 

23521  226 
class ordered_semiring = semiring + comm_monoid_add + ordered_cancel_ab_semigroup_add + mult_mono 
227 

228 
instance ordered_semiring \<subseteq> pordered_cancel_semiring .. 

229 

22390  230 
class ordered_semiring_strict = semiring + comm_monoid_add + ordered_cancel_ab_semigroup_add + 
231 
assumes mult_strict_left_mono: "a \<sqsubset> b \<Longrightarrow> \<^loc>0 \<sqsubset> c \<Longrightarrow> c \<^loc>* a \<sqsubset> c \<^loc>* b" 

232 
assumes mult_strict_right_mono: "a \<sqsubset> b \<Longrightarrow> \<^loc>0 \<sqsubset> c \<Longrightarrow> a \<^loc>* c \<sqsubset> b \<^loc>* c" 

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233 

14940  234 
instance ordered_semiring_strict \<subseteq> semiring_0_cancel .. 
235 

23521  236 
instance ordered_semiring_strict \<subseteq> ordered_semiring 
23550  237 
proof 
238 
fix a b c :: 'a 

239 
assume A: "a \<le> b" "0 \<le> c" 

240 
from A show "c * a \<le> c * b" 

241 
unfolding order_le_less 

242 
using mult_strict_left_mono by auto 

243 
from A show "a * c \<le> b * c" 

244 
unfolding order_le_less 

245 
using mult_strict_right_mono by auto 

246 
qed 

14270  247 

22390  248 
class mult_mono1 = times + zero + ord + 
249 
assumes mult_mono: "a \<sqsubseteq> b \<Longrightarrow> \<^loc>0 \<sqsubseteq> c \<Longrightarrow> c \<^loc>* a \<sqsubseteq> c \<^loc>* b" 

14270  250 

22390  251 
class pordered_comm_semiring = comm_semiring_0 
252 
+ pordered_ab_semigroup_add + mult_mono1 

14270  253 

22390  254 
class pordered_cancel_comm_semiring = comm_semiring_0_cancel 
255 
+ pordered_ab_semigroup_add + mult_mono1 

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256 

14738  257 
instance pordered_cancel_comm_semiring \<subseteq> pordered_comm_semiring .. 
14270  258 

22390  259 
class ordered_comm_semiring_strict = comm_semiring_0 + ordered_cancel_ab_semigroup_add + 
260 
assumes mult_strict_mono: "a \<sqsubset> b \<Longrightarrow> \<^loc>0 \<sqsubset> c \<Longrightarrow> c \<^loc>* a \<sqsubset> c \<^loc>* b" 

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14738  262 
instance pordered_comm_semiring \<subseteq> pordered_semiring 
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263 
proof 
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264 
fix a b c :: 'a 
23550  265 
assume "a \<le> b" "0 \<le> c" 
266 
thus "c * a \<le> c * b" by (rule mult_mono) 

267 
thus "a * c \<le> b * c" by (simp only: mult_commute) 

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268 
qed 
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269 

14738  270 
instance pordered_cancel_comm_semiring \<subseteq> pordered_cancel_semiring .. 
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271 

14738  272 
instance ordered_comm_semiring_strict \<subseteq> ordered_semiring_strict 
23550  273 
proof 
274 
fix a b c :: 'a 

275 
assume "a < b" "0 < c" 

276 
thus "c * a < c * b" by (rule mult_strict_mono) 

277 
thus "a * c < b * c" by (simp only: mult_commute) 

278 
qed 

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279 

14738  280 
instance ordered_comm_semiring_strict \<subseteq> pordered_cancel_comm_semiring 
23550  281 
proof 
282 
fix a b c :: 'a 

283 
assume "a \<le> b" "0 \<le> c" 

284 
thus "c * a \<le> c * b" 

285 
unfolding order_le_less 

286 
using mult_strict_mono by auto 

287 
qed 

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288 

22390  289 
class pordered_ring = ring + pordered_cancel_semiring 
14270  290 

14738  291 
instance pordered_ring \<subseteq> pordered_ab_group_add .. 
14270  292 

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293 
class lordered_ring = pordered_ring + lordered_ab_group_abs 
14270  294 

14940  295 
instance lordered_ring \<subseteq> lordered_ab_group_meet .. 
296 

297 
instance lordered_ring \<subseteq> lordered_ab_group_join .. 

298 

22390  299 
class abs_if = minus + ord + zero + 
300 
assumes abs_if: "abs a = (if a \<sqsubset> 0 then (uminus a) else a)" 

14270  301 

23521  302 
(* The "strict" suffix can be seen as describing the combination of ordered_ring and no_zero_divisors. 
303 
Basically, ordered_ring + no_zero_divisors = ordered_ring_strict. 

304 
*) 

305 
class ordered_ring = ring + ordered_semiring + lordered_ab_group + abs_if 

14270  306 

23550  307 
instance ordered_ring \<subseteq> lordered_ring 
308 
proof 

309 
fix x :: 'a 

310 
show "\<bar>x\<bar> = sup x ( x)" 

311 
by (simp only: abs_if sup_eq_if) 

312 
qed 

23521  313 

314 
class ordered_ring_strict = ring + ordered_semiring_strict + lordered_ab_group + abs_if 

315 

316 
instance ordered_ring_strict \<subseteq> ordered_ring .. 

14270  317 

22390  318 
class pordered_comm_ring = comm_ring + pordered_comm_semiring 
14270  319 

23527  320 
instance pordered_comm_ring \<subseteq> pordered_ring .. 
321 

23073  322 
instance pordered_comm_ring \<subseteq> pordered_cancel_comm_semiring .. 
323 

22390  324 
class ordered_semidom = comm_semiring_1_cancel + ordered_comm_semiring_strict + 
325 
(*previously ordered_semiring*) 

326 
assumes zero_less_one [simp]: "\<^loc>0 \<sqsubset> \<^loc>1" 

14270  327 

23521  328 
class ordered_idom = comm_ring_1 + ordered_comm_semiring_strict + lordered_ab_group + abs_if 
22390  329 
(*previously ordered_ring*) 
14270  330 

14738  331 
instance ordered_idom \<subseteq> ordered_ring_strict .. 
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23073  333 
instance ordered_idom \<subseteq> pordered_comm_ring .. 
334 

22390  335 
class ordered_field = field + ordered_idom 
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336 

15923  337 
lemmas linorder_neqE_ordered_idom = 
338 
linorder_neqE[where 'a = "?'b::ordered_idom"] 

339 

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lemma eq_add_iff1: 
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341 
"(a*e + c = b*e + d) = ((ab)*e + c = (d::'a::ring))" 
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342 
by (simp add: ring_simps) 
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343 

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lemma eq_add_iff2: 
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345 
"(a*e + c = b*e + d) = (c = (ba)*e + (d::'a::ring))" 
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346 
by (simp add: ring_simps) 
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347 

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348 
lemma less_add_iff1: 
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349 
"(a*e + c < b*e + d) = ((ab)*e + c < (d::'a::pordered_ring))" 
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350 
by (simp add: ring_simps) 
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351 

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352 
lemma less_add_iff2: 
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353 
"(a*e + c < b*e + d) = (c < (ba)*e + (d::'a::pordered_ring))" 
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354 
by (simp add: ring_simps) 
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355 

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356 
lemma le_add_iff1: 
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357 
"(a*e + c \<le> b*e + d) = ((ab)*e + c \<le> (d::'a::pordered_ring))" 
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358 
by (simp add: ring_simps) 
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359 

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360 
lemma le_add_iff2: 
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361 
"(a*e + c \<le> b*e + d) = (c \<le> (ba)*e + (d::'a::pordered_ring))" 
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362 
by (simp add: ring_simps) 
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363 

23389  364 

14270  365 
subsection {* Ordering Rules for Multiplication *} 
366 

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367 
lemma mult_left_le_imp_le: 
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368 
"[c*a \<le> c*b; 0 < c] ==> a \<le> (b::'a::ordered_semiring_strict)" 
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369 
by (force simp add: mult_strict_left_mono linorder_not_less [symmetric]) 
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370 

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371 
lemma mult_right_le_imp_le: 
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372 
"[a*c \<le> b*c; 0 < c] ==> a \<le> (b::'a::ordered_semiring_strict)" 
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373 
by (force simp add: mult_strict_right_mono linorder_not_less [symmetric]) 
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374 

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375 
lemma mult_left_less_imp_less: 
23521  376 
"[c*a < c*b; 0 \<le> c] ==> a < (b::'a::ordered_semiring)" 
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377 
by (force simp add: mult_left_mono linorder_not_le [symmetric]) 
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378 

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379 
lemma mult_right_less_imp_less: 
23521  380 
"[a*c < b*c; 0 \<le> c] ==> a < (b::'a::ordered_semiring)" 
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381 
by (force simp add: mult_right_mono linorder_not_le [symmetric]) 
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382 

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383 
lemma mult_strict_left_mono_neg: 
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384 
"[b < a; c < 0] ==> c * a < c * (b::'a::ordered_ring_strict)" 
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385 
apply (drule mult_strict_left_mono [of _ _ "c"]) 
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386 
apply (simp_all add: minus_mult_left [symmetric]) 
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387 
done 
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388 

14738  389 
lemma mult_left_mono_neg: 
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390 
"[b \<le> a; c \<le> 0] ==> c * a \<le> c * (b::'a::pordered_ring)" 
14738  391 
apply (drule mult_left_mono [of _ _ "c"]) 
392 
apply (simp_all add: minus_mult_left [symmetric]) 

393 
done 

394 

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395 
lemma mult_strict_right_mono_neg: 
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396 
"[b < a; c < 0] ==> a * c < b * (c::'a::ordered_ring_strict)" 
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397 
apply (drule mult_strict_right_mono [of _ _ "c"]) 
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398 
apply (simp_all add: minus_mult_right [symmetric]) 
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399 
done 
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400 

14738  401 
lemma mult_right_mono_neg: 
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402 
"[b \<le> a; c \<le> 0] ==> a * c \<le> (b::'a::pordered_ring) * c" 
14738  403 
apply (drule mult_right_mono [of _ _ "c"]) 
404 
apply (simp) 

405 
apply (simp_all add: minus_mult_right [symmetric]) 

406 
done 

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407 

23389  408 

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409 
subsection{* Products of Signs *} 
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410 

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411 
lemma mult_pos_pos: "[ (0::'a::ordered_semiring_strict) < a; 0 < b ] ==> 0 < a*b" 
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412 
by (drule mult_strict_left_mono [of 0 b], auto) 
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413 

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changeset

414 
lemma mult_nonneg_nonneg: "[ (0::'a::pordered_cancel_semiring) \<le> a; 0 \<le> b ] ==> 0 \<le> a*b" 
14738  415 
by (drule mult_left_mono [of 0 b], auto) 
416 

417 
lemma mult_pos_neg: "[ (0::'a::ordered_semiring_strict) < a; b < 0 ] ==> a*b < 0" 

14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

418 
by (drule mult_strict_left_mono [of b 0], auto) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

419 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

420 
lemma mult_nonneg_nonpos: "[ (0::'a::pordered_cancel_semiring) \<le> a; b \<le> 0 ] ==> a*b \<le> 0" 
14738  421 
by (drule mult_left_mono [of b 0], auto) 
422 

423 
lemma mult_pos_neg2: "[ (0::'a::ordered_semiring_strict) < a; b < 0 ] ==> b*a < 0" 

424 
by (drule mult_strict_right_mono[of b 0], auto) 

425 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

426 
lemma mult_nonneg_nonpos2: "[ (0::'a::pordered_cancel_semiring) \<le> a; b \<le> 0 ] ==> b*a \<le> 0" 
14738  427 
by (drule mult_right_mono[of b 0], auto) 
428 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

429 
lemma mult_neg_neg: "[ a < (0::'a::ordered_ring_strict); b < 0 ] ==> 0 < a*b" 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

430 
by (drule mult_strict_right_mono_neg, auto) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

431 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

432 
lemma mult_nonpos_nonpos: "[ a \<le> (0::'a::pordered_ring); b \<le> 0 ] ==> 0 \<le> a*b" 
14738  433 
by (drule mult_right_mono_neg[of a 0 b ], auto) 
434 

14341
a09441bd4f1e
Ring_and_Field now requires axiom add_left_imp_eq for semirings.
paulson
parents:
14334
diff
changeset

435 
lemma zero_less_mult_pos: 
14738  436 
"[ 0 < a*b; 0 < a] ==> 0 < (b::'a::ordered_semiring_strict)" 
21328  437 
apply (cases "b\<le>0") 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

438 
apply (auto simp add: order_le_less linorder_not_less) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

439 
apply (drule_tac mult_pos_neg [of a b]) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

440 
apply (auto dest: order_less_not_sym) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

441 
done 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

442 

14738  443 
lemma zero_less_mult_pos2: 
444 
"[ 0 < b*a; 0 < a] ==> 0 < (b::'a::ordered_semiring_strict)" 

21328  445 
apply (cases "b\<le>0") 
14738  446 
apply (auto simp add: order_le_less linorder_not_less) 
447 
apply (drule_tac mult_pos_neg2 [of a b]) 

448 
apply (auto dest: order_less_not_sym) 

449 
done 

450 

14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

451 
lemma zero_less_mult_iff: 
14738  452 
"((0::'a::ordered_ring_strict) < a*b) = (0 < a & 0 < b  a < 0 & b < 0)" 
16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

453 
apply (auto simp add: order_le_less linorder_not_less mult_pos_pos 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

454 
mult_neg_neg) 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

455 
apply (blast dest: zero_less_mult_pos) 
14738  456 
apply (blast dest: zero_less_mult_pos2) 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

457 
done 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

458 

22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

459 
lemma mult_eq_0_iff [simp]: 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

460 
fixes a b :: "'a::ring_no_zero_divisors" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

461 
shows "(a * b = 0) = (a = 0 \<or> b = 0)" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

462 
by (cases "a = 0 \<or> b = 0", auto dest: no_zero_divisors) 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

463 

775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

464 
instance ordered_ring_strict \<subseteq> ring_no_zero_divisors 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

465 
apply intro_classes 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

466 
apply (auto simp add: linorder_not_less order_le_less linorder_neq_iff) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

467 
apply (force dest: mult_strict_right_mono_neg mult_strict_right_mono)+ 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

468 
done 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

469 

95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

470 
lemma zero_le_mult_iff: 
14738  471 
"((0::'a::ordered_ring_strict) \<le> a*b) = (0 \<le> a & 0 \<le> b  a \<le> 0 & b \<le> 0)" 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

472 
by (auto simp add: eq_commute [of 0] order_le_less linorder_not_less 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

473 
zero_less_mult_iff) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

474 

95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

475 
lemma mult_less_0_iff: 
14738  476 
"(a*b < (0::'a::ordered_ring_strict)) = (0 < a & b < 0  a < 0 & 0 < b)" 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

477 
apply (insert zero_less_mult_iff [of "a" b]) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

478 
apply (force simp add: minus_mult_left[symmetric]) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

479 
done 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

480 

95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

481 
lemma mult_le_0_iff: 
14738  482 
"(a*b \<le> (0::'a::ordered_ring_strict)) = (0 \<le> a & b \<le> 0  a \<le> 0 & 0 \<le> b)" 
14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

483 
apply (insert zero_le_mult_iff [of "a" b]) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

484 
apply (force simp add: minus_mult_left[symmetric]) 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

485 
done 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

486 

14738  487 
lemma split_mult_pos_le: "(0 \<le> a & 0 \<le> b)  (a \<le> 0 & b \<le> 0) \<Longrightarrow> 0 \<le> a * (b::_::pordered_ring)" 
16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

488 
by (auto simp add: mult_nonneg_nonneg mult_nonpos_nonpos) 
14738  489 

490 
lemma split_mult_neg_le: "(0 \<le> a & b \<le> 0)  (a \<le> 0 & 0 \<le> b) \<Longrightarrow> a * b \<le> (0::_::pordered_cancel_semiring)" 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

491 
by (auto simp add: mult_nonneg_nonpos mult_nonneg_nonpos2) 
14738  492 

23095  493 
lemma zero_le_square[simp]: "(0::'a::ordered_ring_strict) \<le> a*a" 
494 
by (simp add: zero_le_mult_iff linorder_linear) 

495 

496 
lemma not_square_less_zero[simp]: "\<not> (a * a < (0::'a::ordered_ring_strict))" 

497 
by (simp add: not_less) 

14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

498 

14738  499 
text{*Proving axiom @{text zero_less_one} makes all @{text ordered_semidom} 
500 
theorems available to members of @{term ordered_idom} *} 

501 

502 
instance ordered_idom \<subseteq> ordered_semidom 

14421
ee97b6463cb4
new Ring_and_Field hierarchy, eliminating redundant axioms
paulson
parents:
14398
diff
changeset

503 
proof 
ee97b6463cb4
new Ring_and_Field hierarchy, eliminating redundant axioms
paulson
parents:
14398
diff
changeset

504 
have "(0::'a) \<le> 1*1" by (rule zero_le_square) 
14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

505 
thus "(0::'a) < 1" by (simp add: order_le_less) 
14421
ee97b6463cb4
new Ring_and_Field hierarchy, eliminating redundant axioms
paulson
parents:
14398
diff
changeset

506 
qed 
ee97b6463cb4
new Ring_and_Field hierarchy, eliminating redundant axioms
paulson
parents:
14398
diff
changeset

507 

14738  508 
instance ordered_idom \<subseteq> idom .. 
509 

14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

510 
text{*All three types of comparision involving 0 and 1 are covered.*} 
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

511 

17085  512 
lemmas one_neq_zero = zero_neq_one [THEN not_sym] 
513 
declare one_neq_zero [simp] 

14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

514 

14738  515 
lemma zero_le_one [simp]: "(0::'a::ordered_semidom) \<le> 1" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

516 
by (rule zero_less_one [THEN order_less_imp_le]) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

517 

14738  518 
lemma not_one_le_zero [simp]: "~ (1::'a::ordered_semidom) \<le> 0" 
519 
by (simp add: linorder_not_le) 

14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

520 

14738  521 
lemma not_one_less_zero [simp]: "~ (1::'a::ordered_semidom) < 0" 
522 
by (simp add: linorder_not_less) 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

523 

23389  524 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

525 
subsection{*More Monotonicity*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

526 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

527 
text{*Strict monotonicity in both arguments*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

528 
lemma mult_strict_mono: 
14738  529 
"[a<b; c<d; 0<b; 0\<le>c] ==> a * c < b * (d::'a::ordered_semiring_strict)" 
21328  530 
apply (cases "c=0") 
16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

531 
apply (simp add: mult_pos_pos) 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

532 
apply (erule mult_strict_right_mono [THEN order_less_trans]) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

533 
apply (force simp add: order_le_less) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

534 
apply (erule mult_strict_left_mono, assumption) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

535 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

536 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

537 
text{*This weaker variant has more natural premises*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

538 
lemma mult_strict_mono': 
14738  539 
"[ a<b; c<d; 0 \<le> a; 0 \<le> c] ==> a * c < b * (d::'a::ordered_semiring_strict)" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

540 
apply (rule mult_strict_mono) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

541 
apply (blast intro: order_le_less_trans)+ 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

542 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

543 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

544 
lemma mult_mono: 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

545 
"[a \<le> b; c \<le> d; 0 \<le> b; 0 \<le> c] 
14738  546 
==> a * c \<le> b * (d::'a::pordered_semiring)" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

547 
apply (erule mult_right_mono [THEN order_trans], assumption) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

548 
apply (erule mult_left_mono, assumption) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

549 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

550 

21258  551 
lemma mult_mono': 
552 
"[a \<le> b; c \<le> d; 0 \<le> a; 0 \<le> c] 

553 
==> a * c \<le> b * (d::'a::pordered_semiring)" 

554 
apply (rule mult_mono) 

555 
apply (fast intro: order_trans)+ 

556 
done 

557 

14738  558 
lemma less_1_mult: "[ 1 < m; 1 < n ] ==> 1 < m*(n::'a::ordered_semidom)" 
14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

559 
apply (insert mult_strict_mono [of 1 m 1 n]) 
14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

560 
apply (simp add: order_less_trans [OF zero_less_one]) 
14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

561 
done 
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

562 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

563 
lemma mult_less_le_imp_less: "(a::'a::ordered_semiring_strict) < b ==> 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

564 
c <= d ==> 0 <= a ==> 0 < c ==> a * c < b * d" 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

565 
apply (subgoal_tac "a * c < b * c") 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

566 
apply (erule order_less_le_trans) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

567 
apply (erule mult_left_mono) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

568 
apply simp 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

569 
apply (erule mult_strict_right_mono) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

570 
apply assumption 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

571 
done 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

572 

c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

573 
lemma mult_le_less_imp_less: "(a::'a::ordered_semiring_strict) <= b ==> 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

574 
c < d ==> 0 < a ==> 0 <= c ==> a * c < b * d" 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

575 
apply (subgoal_tac "a * c <= b * c") 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

576 
apply (erule order_le_less_trans) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

577 
apply (erule mult_strict_left_mono) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

578 
apply simp 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

579 
apply (erule mult_right_mono) 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

580 
apply simp 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

581 
done 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

582 

23389  583 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

584 
subsection{*Cancellation Laws for Relationships With a Common Factor*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

585 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

586 
text{*Cancellation laws for @{term "c*a < c*b"} and @{term "a*c < b*c"}, 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

587 
also with the relations @{text "\<le>"} and equality.*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

588 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

589 
text{*These ``disjunction'' versions produce two cases when the comparison is 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

590 
an assumption, but effectively four when the comparison is a goal.*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

591 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

592 
lemma mult_less_cancel_right_disj: 
14738  593 
"(a*c < b*c) = ((0 < c & a < b)  (c < 0 & b < (a::'a::ordered_ring_strict)))" 
21328  594 
apply (cases "c = 0") 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

595 
apply (auto simp add: linorder_neq_iff mult_strict_right_mono 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

596 
mult_strict_right_mono_neg) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

597 
apply (auto simp add: linorder_not_less 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

598 
linorder_not_le [symmetric, of "a*c"] 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

599 
linorder_not_le [symmetric, of a]) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

600 
apply (erule_tac [!] notE) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

601 
apply (auto simp add: order_less_imp_le mult_right_mono 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

602 
mult_right_mono_neg) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

603 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

604 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

605 
lemma mult_less_cancel_left_disj: 
14738  606 
"(c*a < c*b) = ((0 < c & a < b)  (c < 0 & b < (a::'a::ordered_ring_strict)))" 
21328  607 
apply (cases "c = 0") 
14738  608 
apply (auto simp add: linorder_neq_iff mult_strict_left_mono 
609 
mult_strict_left_mono_neg) 

610 
apply (auto simp add: linorder_not_less 

611 
linorder_not_le [symmetric, of "c*a"] 

612 
linorder_not_le [symmetric, of a]) 

613 
apply (erule_tac [!] notE) 

614 
apply (auto simp add: order_less_imp_le mult_left_mono 

615 
mult_left_mono_neg) 

616 
done 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

617 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

618 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

619 
text{*The ``conjunction of implication'' lemmas produce two cases when the 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

620 
comparison is a goal, but give four when the comparison is an assumption.*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

621 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

622 
lemma mult_less_cancel_right: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

623 
fixes c :: "'a :: ordered_ring_strict" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

624 
shows "(a*c < b*c) = ((0 \<le> c > a < b) & (c \<le> 0 > b < a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

625 
by (insert mult_less_cancel_right_disj [of a c b], auto) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

626 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

627 
lemma mult_less_cancel_left: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

628 
fixes c :: "'a :: ordered_ring_strict" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

629 
shows "(c*a < c*b) = ((0 \<le> c > a < b) & (c \<le> 0 > b < a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

630 
by (insert mult_less_cancel_left_disj [of c a b], auto) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

631 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

632 
lemma mult_le_cancel_right: 
14738  633 
"(a*c \<le> b*c) = ((0<c > a\<le>b) & (c<0 > b \<le> (a::'a::ordered_ring_strict)))" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

634 
by (simp add: linorder_not_less [symmetric] mult_less_cancel_right_disj) 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

635 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

636 
lemma mult_le_cancel_left: 
14738  637 
"(c*a \<le> c*b) = ((0<c > a\<le>b) & (c<0 > b \<le> (a::'a::ordered_ring_strict)))" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

638 
by (simp add: linorder_not_less [symmetric] mult_less_cancel_left_disj) 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

639 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

640 
lemma mult_less_imp_less_left: 
14341
a09441bd4f1e
Ring_and_Field now requires axiom add_left_imp_eq for semirings.
paulson
parents:
14334
diff
changeset

641 
assumes less: "c*a < c*b" and nonneg: "0 \<le> c" 
14738  642 
shows "a < (b::'a::ordered_semiring_strict)" 
14377  643 
proof (rule ccontr) 
644 
assume "~ a < b" 

645 
hence "b \<le> a" by (simp add: linorder_not_less) 

23389  646 
hence "c*b \<le> c*a" using nonneg by (rule mult_left_mono) 
14377  647 
with this and less show False 
648 
by (simp add: linorder_not_less [symmetric]) 

649 
qed 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

650 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

651 
lemma mult_less_imp_less_right: 
14738  652 
assumes less: "a*c < b*c" and nonneg: "0 <= c" 
653 
shows "a < (b::'a::ordered_semiring_strict)" 

654 
proof (rule ccontr) 

655 
assume "~ a < b" 

656 
hence "b \<le> a" by (simp add: linorder_not_less) 

23389  657 
hence "b*c \<le> a*c" using nonneg by (rule mult_right_mono) 
14738  658 
with this and less show False 
659 
by (simp add: linorder_not_less [symmetric]) 

660 
qed 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

661 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

662 
text{*Cancellation of equalities with a common factor*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

663 
lemma mult_cancel_right [simp]: 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

664 
fixes a b c :: "'a::ring_no_zero_divisors" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

665 
shows "(a * c = b * c) = (c = 0 \<or> a = b)" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

666 
proof  
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

667 
have "(a * c = b * c) = ((a  b) * c = 0)" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

668 
by (simp add: ring_distribs) 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

669 
thus ?thesis 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

670 
by (simp add: disj_commute) 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

671 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

672 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

673 
lemma mult_cancel_left [simp]: 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

674 
fixes a b c :: "'a::ring_no_zero_divisors" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

675 
shows "(c * a = c * b) = (c = 0 \<or> a = b)" 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

676 
proof  
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

677 
have "(c * a = c * b) = (c * (a  b) = 0)" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

678 
by (simp add: ring_distribs) 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

679 
thus ?thesis 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

680 
by simp 
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

681 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

682 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

683 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

684 
subsubsection{*Special Cancellation Simprules for Multiplication*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

685 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

686 
text{*These also produce two cases when the comparison is a goal.*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

687 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

688 
lemma mult_le_cancel_right1: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

689 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

690 
shows "(c \<le> b*c) = ((0<c > 1\<le>b) & (c<0 > b \<le> 1))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

691 
by (insert mult_le_cancel_right [of 1 c b], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

692 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

693 
lemma mult_le_cancel_right2: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

694 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

695 
shows "(a*c \<le> c) = ((0<c > a\<le>1) & (c<0 > 1 \<le> a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

696 
by (insert mult_le_cancel_right [of a c 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

697 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

698 
lemma mult_le_cancel_left1: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

699 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

700 
shows "(c \<le> c*b) = ((0<c > 1\<le>b) & (c<0 > b \<le> 1))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

701 
by (insert mult_le_cancel_left [of c 1 b], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

702 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

703 
lemma mult_le_cancel_left2: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

704 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

705 
shows "(c*a \<le> c) = ((0<c > a\<le>1) & (c<0 > 1 \<le> a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

706 
by (insert mult_le_cancel_left [of c a 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

707 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

708 
lemma mult_less_cancel_right1: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

709 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

710 
shows "(c < b*c) = ((0 \<le> c > 1<b) & (c \<le> 0 > b < 1))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

711 
by (insert mult_less_cancel_right [of 1 c b], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

712 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

713 
lemma mult_less_cancel_right2: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

714 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

715 
shows "(a*c < c) = ((0 \<le> c > a<1) & (c \<le> 0 > 1 < a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

716 
by (insert mult_less_cancel_right [of a c 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

717 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

718 
lemma mult_less_cancel_left1: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

719 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

720 
shows "(c < c*b) = ((0 \<le> c > 1<b) & (c \<le> 0 > b < 1))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

721 
by (insert mult_less_cancel_left [of c 1 b], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

722 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

723 
lemma mult_less_cancel_left2: 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

724 
fixes c :: "'a :: ordered_idom" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

725 
shows "(c*a < c) = ((0 \<le> c > a<1) & (c \<le> 0 > 1 < a))" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

726 
by (insert mult_less_cancel_left [of c a 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

727 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

728 
lemma mult_cancel_right1 [simp]: 
23544  729 
fixes c :: "'a :: ring_1_no_zero_divisors" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

730 
shows "(c = b*c) = (c = 0  b=1)" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

731 
by (insert mult_cancel_right [of 1 c b], force) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

732 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

733 
lemma mult_cancel_right2 [simp]: 
23544  734 
fixes c :: "'a :: ring_1_no_zero_divisors" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

735 
shows "(a*c = c) = (c = 0  a=1)" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

736 
by (insert mult_cancel_right [of a c 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

737 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

738 
lemma mult_cancel_left1 [simp]: 
23544  739 
fixes c :: "'a :: ring_1_no_zero_divisors" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

740 
shows "(c = c*b) = (c = 0  b=1)" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

741 
by (insert mult_cancel_left [of c 1 b], force) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

742 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

743 
lemma mult_cancel_left2 [simp]: 
23544  744 
fixes c :: "'a :: ring_1_no_zero_divisors" 
15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

745 
shows "(c*a = c) = (c = 0  a=1)" 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

746 
by (insert mult_cancel_left [of c a 1], simp) 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

747 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

748 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

749 
text{*Simprules for comparisons where common factors can be cancelled.*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

750 
lemmas mult_compare_simps = 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

751 
mult_le_cancel_right mult_le_cancel_left 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

752 
mult_le_cancel_right1 mult_le_cancel_right2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

753 
mult_le_cancel_left1 mult_le_cancel_left2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

754 
mult_less_cancel_right mult_less_cancel_left 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

755 
mult_less_cancel_right1 mult_less_cancel_right2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

756 
mult_less_cancel_left1 mult_less_cancel_left2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

757 
mult_cancel_right mult_cancel_left 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

758 
mult_cancel_right1 mult_cancel_right2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

759 
mult_cancel_left1 mult_cancel_left2 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

760 

ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

761 

14265
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

762 
subsection {* Fields *} 
95b42e69436c
HOL: installation of Ring_and_Field as the basis for Naturals and Reals
paulson
parents:
diff
changeset

763 

14288  764 
lemma right_inverse_eq: "b \<noteq> 0 ==> (a / b = 1) = (a = (b::'a::field))" 
765 
proof 

766 
assume neq: "b \<noteq> 0" 

767 
{ 

768 
hence "a = (a / b) * b" by (simp add: divide_inverse mult_ac) 

769 
also assume "a / b = 1" 

770 
finally show "a = b" by simp 

771 
next 

772 
assume "a = b" 

773 
with neq show "a / b = 1" by (simp add: divide_inverse) 

774 
} 

775 
qed 

776 

777 
lemma nonzero_inverse_eq_divide: "a \<noteq> 0 ==> inverse (a::'a::field) = 1/a" 

778 
by (simp add: divide_inverse) 

779 

23398  780 
lemma divide_self[simp]: "a \<noteq> 0 ==> a / (a::'a::field) = 1" 
14288  781 
by (simp add: divide_inverse) 
782 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

783 
lemma divide_zero [simp]: "a / 0 = (0::'a::{field,division_by_zero})" 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

784 
by (simp add: divide_inverse) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

785 

15228  786 
lemma divide_self_if [simp]: 
787 
"a / (a::'a::{field,division_by_zero}) = (if a=0 then 0 else 1)" 

788 
by (simp add: divide_self) 

789 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

790 
lemma divide_zero_left [simp]: "0/a = (0::'a::field)" 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

791 
by (simp add: divide_inverse) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

792 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

793 
lemma inverse_eq_divide: "inverse (a::'a::field) = 1/a" 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

794 
by (simp add: divide_inverse) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

795 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

796 
lemma add_divide_distrib: "(a+b)/(c::'a::field) = a/c + b/c" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

797 
by (simp add: divide_inverse ring_distribs) 
14293  798 

23482  799 
(* what ordering?? this is a straight instance of mult_eq_0_iff 
14270  800 
text{*Compared with @{text mult_eq_0_iff}, this version removes the requirement 
801 
of an ordering.*} 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

802 
lemma field_mult_eq_0_iff [simp]: 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

803 
"(a*b = (0::'a::division_ring)) = (a = 0  b = 0)" 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

804 
by simp 
23482  805 
*) 
23496  806 
(* subsumed by mult_cancel lemmas on ring_no_zero_divisors 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

807 
text{*Cancellation of equalities with a common factor*} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

808 
lemma field_mult_cancel_right_lemma: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

809 
assumes cnz: "c \<noteq> (0::'a::division_ring)" 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

810 
and eq: "a*c = b*c" 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

811 
shows "a=b" 
14377  812 
proof  
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

813 
have "(a * c) * inverse c = (b * c) * inverse c" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

814 
by (simp add: eq) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

815 
thus "a=b" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

816 
by (simp add: mult_assoc cnz) 
14377  817 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

818 

14348
744c868ee0b7
Defining the type class "ringpower" and deleting superseded theorems for
paulson
parents:
14341
diff
changeset

819 
lemma field_mult_cancel_right [simp]: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

820 
"(a*c = b*c) = (c = (0::'a::division_ring)  a=b)" 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

821 
by simp 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

822 

14348
744c868ee0b7
Defining the type class "ringpower" and deleting superseded theorems for
paulson
parents:
14341
diff
changeset

823 
lemma field_mult_cancel_left [simp]: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

824 
"(c*a = c*b) = (c = (0::'a::division_ring)  a=b)" 
22990
775e9de3db48
added classes ring_no_zero_divisors and dom (noncommutative version of idom);
huffman
parents:
22987
diff
changeset

825 
by simp 
23496  826 
*) 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

827 
lemma nonzero_imp_inverse_nonzero: 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

828 
"a \<noteq> 0 ==> inverse a \<noteq> (0::'a::division_ring)" 
14377  829 
proof 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

830 
assume ianz: "inverse a = 0" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

831 
assume "a \<noteq> 0" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

832 
hence "1 = a * inverse a" by simp 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

833 
also have "... = 0" by (simp add: ianz) 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

834 
finally have "1 = (0::'a::division_ring)" . 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

835 
thus False by (simp add: eq_commute) 
14377  836 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

837 

14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

838 

ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

839 
subsection{*Basic Properties of @{term inverse}*} 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

840 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

841 
lemma inverse_zero_imp_zero: "inverse a = 0 ==> a = (0::'a::division_ring)" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

842 
apply (rule ccontr) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

843 
apply (blast dest: nonzero_imp_inverse_nonzero) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

844 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

845 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

846 
lemma inverse_nonzero_imp_nonzero: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

847 
"inverse a = 0 ==> a = (0::'a::division_ring)" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

848 
apply (rule ccontr) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

849 
apply (blast dest: nonzero_imp_inverse_nonzero) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

850 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

851 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

852 
lemma inverse_nonzero_iff_nonzero [simp]: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

853 
"(inverse a = 0) = (a = (0::'a::{division_ring,division_by_zero}))" 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

854 
by (force dest: inverse_nonzero_imp_nonzero) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

855 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

856 
lemma nonzero_inverse_minus_eq: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

857 
assumes [simp]: "a\<noteq>0" 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

858 
shows "inverse(a) = inverse(a::'a::division_ring)" 
14377  859 
proof  
860 
have "a * inverse ( a) = a *  inverse a" 

861 
by simp 

862 
thus ?thesis 

23496  863 
by (simp only: mult_cancel_left, simp) 
14377  864 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

865 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

866 
lemma inverse_minus_eq [simp]: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

867 
"inverse(a) = inverse(a::'a::{division_ring,division_by_zero})" 
14377  868 
proof cases 
869 
assume "a=0" thus ?thesis by (simp add: inverse_zero) 

870 
next 

871 
assume "a\<noteq>0" 

872 
thus ?thesis by (simp add: nonzero_inverse_minus_eq) 

873 
qed 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

874 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

875 
lemma nonzero_inverse_eq_imp_eq: 
14269  876 
assumes inveq: "inverse a = inverse b" 
877 
and anz: "a \<noteq> 0" 

878 
and bnz: "b \<noteq> 0" 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

879 
shows "a = (b::'a::division_ring)" 
14377  880 
proof  
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

881 
have "a * inverse b = a * inverse a" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

882 
by (simp add: inveq) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

883 
hence "(a * inverse b) * b = (a * inverse a) * b" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

884 
by simp 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

885 
thus "a = b" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

886 
by (simp add: mult_assoc anz bnz) 
14377  887 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

888 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

889 
lemma inverse_eq_imp_eq: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

890 
"inverse a = inverse b ==> a = (b::'a::{division_ring,division_by_zero})" 
21328  891 
apply (cases "a=0  b=0") 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

892 
apply (force dest!: inverse_zero_imp_zero 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

893 
simp add: eq_commute [of "0::'a"]) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

894 
apply (force dest!: nonzero_inverse_eq_imp_eq) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

895 
done 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

896 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

897 
lemma inverse_eq_iff_eq [simp]: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

898 
"(inverse a = inverse b) = (a = (b::'a::{division_ring,division_by_zero}))" 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

899 
by (force dest!: inverse_eq_imp_eq) 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

900 

14270  901 
lemma nonzero_inverse_inverse_eq: 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

902 
assumes [simp]: "a \<noteq> 0" 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

903 
shows "inverse(inverse (a::'a::division_ring)) = a" 
14270  904 
proof  
905 
have "(inverse (inverse a) * inverse a) * a = a" 

906 
by (simp add: nonzero_imp_inverse_nonzero) 

907 
thus ?thesis 

908 
by (simp add: mult_assoc) 

909 
qed 

910 

911 
lemma inverse_inverse_eq [simp]: 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

912 
"inverse(inverse (a::'a::{division_ring,division_by_zero})) = a" 
14270  913 
proof cases 
914 
assume "a=0" thus ?thesis by simp 

915 
next 

916 
assume "a\<noteq>0" 

917 
thus ?thesis by (simp add: nonzero_inverse_inverse_eq) 

918 
qed 

919 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

920 
lemma inverse_1 [simp]: "inverse 1 = (1::'a::division_ring)" 
14270  921 
proof  
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

922 
have "inverse 1 * 1 = (1::'a::division_ring)" 
14270  923 
by (rule left_inverse [OF zero_neq_one [symmetric]]) 
924 
thus ?thesis by simp 

925 
qed 

926 

15077
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

927 
lemma inverse_unique: 
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

928 
assumes ab: "a*b = 1" 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

929 
shows "inverse a = (b::'a::division_ring)" 
15077
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

930 
proof  
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

931 
have "a \<noteq> 0" using ab by auto 
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

932 
moreover have "inverse a * (a * b) = inverse a" by (simp add: ab) 
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

933 
ultimately show ?thesis by (simp add: mult_assoc [symmetric]) 
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

934 
qed 
89840837108e
converting Hyperreal/Transcendental to Isar script
paulson
parents:
15010
diff
changeset

935 

14270  936 
lemma nonzero_inverse_mult_distrib: 
937 
assumes anz: "a \<noteq> 0" 

938 
and bnz: "b \<noteq> 0" 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

939 
shows "inverse(a*b) = inverse(b) * inverse(a::'a::division_ring)" 
14270  940 
proof  
941 
have "inverse(a*b) * (a * b) * inverse(b) = inverse(b)" 

23482  942 
by (simp add: anz bnz) 
14270  943 
hence "inverse(a*b) * a = inverse(b)" 
944 
by (simp add: mult_assoc bnz) 

945 
hence "inverse(a*b) * a * inverse(a) = inverse(b) * inverse(a)" 

946 
by simp 

947 
thus ?thesis 

948 
by (simp add: mult_assoc anz) 

949 
qed 

950 

951 
text{*This version builds in division by zero while also reorienting 

952 
the righthand side.*} 

953 
lemma inverse_mult_distrib [simp]: 

954 
"inverse(a*b) = inverse(a) * inverse(b::'a::{field,division_by_zero})" 

955 
proof cases 

956 
assume "a \<noteq> 0 & b \<noteq> 0" 

22993  957 
thus ?thesis 
958 
by (simp add: nonzero_inverse_mult_distrib mult_commute) 

14270  959 
next 
960 
assume "~ (a \<noteq> 0 & b \<noteq> 0)" 

22993  961 
thus ?thesis 
962 
by force 

14270  963 
qed 
964 

20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

965 
lemma division_ring_inverse_add: 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

966 
"[(a::'a::division_ring) \<noteq> 0; b \<noteq> 0] 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

967 
==> inverse a + inverse b = inverse a * (a+b) * inverse b" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

968 
by (simp add: ring_simps) 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

969 

23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

970 
lemma division_ring_inverse_diff: 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

971 
"[(a::'a::division_ring) \<noteq> 0; b \<noteq> 0] 
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

972 
==> inverse a  inverse b = inverse a * (ba) * inverse b" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

973 
by (simp add: ring_simps) 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

974 

14270  975 
text{*There is no slick version using division by zero.*} 
976 
lemma inverse_add: 

23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

977 
"[a \<noteq> 0; b \<noteq> 0] 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

978 
==> inverse a + inverse b = (a+b) * inverse a * inverse (b::'a::field)" 
20496
23eb6034c06d
added axclass division_ring (like field without commutativity; includes e.g. quaternions) and generalized some theorems from field to division_ring
huffman
parents:
19404
diff
changeset

979 
by (simp add: division_ring_inverse_add mult_ac) 
14270  980 

14365
3d4df8c166ae
replacing HOL/Real/PRat, PNat by the rational number development
paulson
parents:
14353
diff
changeset

981 
lemma inverse_divide [simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

982 
"inverse (a/b) = b / (a::'a::{field,division_by_zero})" 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

983 
by (simp add: divide_inverse mult_commute) 
14365
3d4df8c166ae
replacing HOL/Real/PRat, PNat by the rational number development
paulson
parents:
14353
diff
changeset

984 

23389  985 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

986 
subsection {* Calculations with fractions *} 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

987 

23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

988 
text{* There is a whole bunch of simprules just for class @{text 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

989 
field} but none for class @{text field} and @{text nonzero_divides} 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

990 
because the latter are covered by a simproc. *} 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

991 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

992 
lemma nonzero_mult_divide_mult_cancel_left[simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

993 
assumes [simp]: "b\<noteq>0" and [simp]: "c\<noteq>0" shows "(c*a)/(c*b) = a/(b::'a::field)" 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

994 
proof  
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

995 
have "(c*a)/(c*b) = c * a * (inverse b * inverse c)" 
23482  996 
by (simp add: divide_inverse nonzero_inverse_mult_distrib) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

997 
also have "... = a * inverse b * (inverse c * c)" 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

998 
by (simp only: mult_ac) 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

999 
also have "... = a * inverse b" 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1000 
by simp 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1001 
finally show ?thesis 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1002 
by (simp add: divide_inverse) 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1003 
qed 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1004 

23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1005 
lemma mult_divide_mult_cancel_left: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1006 
"c\<noteq>0 ==> (c*a) / (c*b) = a / (b::'a::{field,division_by_zero})" 
21328  1007 
apply (cases "b = 0") 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1008 
apply (simp_all add: nonzero_mult_divide_mult_cancel_left) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1009 
done 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1010 

23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1011 
lemma nonzero_mult_divide_mult_cancel_right: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1012 
"[b\<noteq>0; c\<noteq>0] ==> (a*c) / (b*c) = a/(b::'a::field)" 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1013 
by (simp add: mult_commute [of _ c] nonzero_mult_divide_mult_cancel_left) 
14321  1014 

23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1015 
lemma mult_divide_mult_cancel_right: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1016 
"c\<noteq>0 ==> (a*c) / (b*c) = a / (b::'a::{field,division_by_zero})" 
21328  1017 
apply (cases "b = 0") 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1018 
apply (simp_all add: nonzero_mult_divide_mult_cancel_right) 
14321  1019 
done 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1020 

14284
f1abe67c448a
reorganisation of Real/RealArith0.ML; more `Isar scripts
paulson
parents:
14277
diff
changeset

1021 
lemma divide_1 [simp]: "a/1 = (a::'a::field)" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1022 
by (simp add: divide_inverse) 
14284
f1abe67c448a
reorganisation of Real/RealArith0.ML; more `Isar scripts
paulson
parents:
14277
diff
changeset

1023 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

1024 
lemma times_divide_eq_right: "a * (b/c) = (a*b) / (c::'a::field)" 
14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1025 
by (simp add: divide_inverse mult_assoc) 
14288  1026 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1027 
lemma times_divide_eq_left: "(b/c) * a = (b*a) / (c::'a::field)" 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1028 
by (simp add: divide_inverse mult_ac) 
14288  1029 

23482  1030 
lemmas times_divide_eq = times_divide_eq_right times_divide_eq_left 
1031 

14288  1032 
lemma divide_divide_eq_right [simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1033 
"a / (b/c) = (a*c) / (b::'a::{field,division_by_zero})" 
14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1034 
by (simp add: divide_inverse mult_ac) 
14288  1035 

1036 
lemma divide_divide_eq_left [simp]: 

23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1037 
"(a / b) / (c::'a::{field,division_by_zero}) = a / (b*c)" 
14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1038 
by (simp add: divide_inverse mult_assoc) 
14288  1039 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

1040 
lemma add_frac_eq: "(y::'a::field) ~= 0 ==> z ~= 0 ==> 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

1041 
x / y + w / z = (x * z + w * y) / (y * z)" 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1042 
apply (subgoal_tac "x / y = (x * z) / (y * z)") 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1043 
apply (erule ssubst) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1044 
apply (subgoal_tac "w / z = (w * y) / (y * z)") 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1045 
apply (erule ssubst) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1046 
apply (rule add_divide_distrib [THEN sym]) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1047 
apply (subst mult_commute) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1048 
apply (erule nonzero_mult_divide_mult_cancel_left [THEN sym]) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1049 
apply assumption 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1050 
apply (erule nonzero_mult_divide_mult_cancel_right [THEN sym]) 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1051 
apply assumption 
16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

1052 
done 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1053 

23389  1054 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

1055 
subsubsection{*Special Cancellation Simprules for Division*} 
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

1056 

23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1057 
lemma mult_divide_mult_cancel_left_if[simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1058 
fixes c :: "'a :: {field,division_by_zero}" 
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1059 
shows "(c*a) / (c*b) = (if c=0 then 0 else a/b)" 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1060 
by (simp add: mult_divide_mult_cancel_left) 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1061 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1062 
lemma nonzero_mult_divide_cancel_right[simp]: 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1063 
"b \<noteq> 0 \<Longrightarrow> a * b / b = (a::'a::field)" 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1064 
using nonzero_mult_divide_mult_cancel_right[of 1 b a] by simp 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1065 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1066 
lemma nonzero_mult_divide_cancel_left[simp]: 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1067 
"a \<noteq> 0 \<Longrightarrow> a * b / a = (b::'a::field)" 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1068 
using nonzero_mult_divide_mult_cancel_left[of 1 a b] by simp 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1069 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1070 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1071 
lemma nonzero_divide_mult_cancel_right[simp]: 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1072 
"\<lbrakk> a\<noteq>0; b\<noteq>0 \<rbrakk> \<Longrightarrow> b / (a * b) = 1/(a::'a::field)" 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1073 
using nonzero_mult_divide_mult_cancel_right[of a b 1] by simp 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1074 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1075 
lemma nonzero_divide_mult_cancel_left[simp]: 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1076 
"\<lbrakk> a\<noteq>0; b\<noteq>0 \<rbrakk> \<Longrightarrow> a / (a * b) = 1/(b::'a::field)" 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1077 
using nonzero_mult_divide_mult_cancel_left[of b a 1] by simp 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1078 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1079 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1080 
lemma nonzero_mult_divide_mult_cancel_left2[simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1081 
"[b\<noteq>0; c\<noteq>0] ==> (c*a) / (b*c) = a/(b::'a::field)" 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1082 
using nonzero_mult_divide_mult_cancel_left[of b c a] by(simp add:mult_ac) 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1083 

5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1084 
lemma nonzero_mult_divide_mult_cancel_right2[simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1085 
"[b\<noteq>0; c\<noteq>0] ==> (a*c) / (c*b) = a/(b::'a::field)" 
23413
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1086 
using nonzero_mult_divide_mult_cancel_right[of b c a] by(simp add:mult_ac) 
5caa2710dd5b
tuned laws for cancellation in divisions for fields.
nipkow
parents:
23406
diff
changeset

1087 

15234
ec91a90c604e
simplification tweaks for better arithmetic reasoning
paulson
parents:
15229
diff
changeset

1088 

14293  1089 
subsection {* Division and Unary Minus *} 
1090 

1091 
lemma nonzero_minus_divide_left: "b \<noteq> 0 ==>  (a/b) = (a) / (b::'a::field)" 

1092 
by (simp add: divide_inverse minus_mult_left) 

1093 

1094 
lemma nonzero_minus_divide_right: "b \<noteq> 0 ==>  (a/b) = a / (b::'a::field)" 

1095 
by (simp add: divide_inverse nonzero_inverse_minus_eq minus_mult_right) 

1096 

1097 
lemma nonzero_minus_divide_divide: "b \<noteq> 0 ==> (a)/(b) = a / (b::'a::field)" 

1098 
by (simp add: divide_inverse nonzero_inverse_minus_eq) 

1099 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1100 
lemma minus_divide_left: " (a/b) = (a) / (b::'a::field)" 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1101 
by (simp add: divide_inverse minus_mult_left [symmetric]) 
14293  1102 

1103 
lemma minus_divide_right: " (a/b) = a / (b::'a::{field,division_by_zero})" 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1104 
by (simp add: divide_inverse minus_mult_right [symmetric]) 
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1105 

14293  1106 

1107 
text{*The effect is to extract signs from divisions*} 

17085  1108 
lemmas divide_minus_left = minus_divide_left [symmetric] 
1109 
lemmas divide_minus_right = minus_divide_right [symmetric] 

1110 
declare divide_minus_left [simp] divide_minus_right [simp] 

14293  1111 

14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

1112 
text{*Also, extract signs from products*} 
17085  1113 
lemmas mult_minus_left = minus_mult_left [symmetric] 
1114 
lemmas mult_minus_right = minus_mult_right [symmetric] 

1115 
declare mult_minus_left [simp] mult_minus_right [simp] 

14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

1116 

14293  1117 
lemma minus_divide_divide [simp]: 
23477
f4b83f03cac9
tuned and renamed group_eq_simps and ring_eq_simps
nipkow
parents:
23413
diff
changeset

1118 
"(a)/(b) = a / (b::'a::{field,division_by_zero})" 
21328  1119 
apply (cases "b=0", simp) 
14293  1120 
apply (simp add: nonzero_minus_divide_divide) 
1121 
done 

1122 

14430
5cb24165a2e1
new material from Avigad, and simplified treatment of division by 0
paulson
parents:
14421
diff
changeset

1123 
lemma diff_divide_distrib: "(ab)/(c::'a::field) = a/c  b/c" 
14387
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

1124 
by (simp add: diff_minus add_divide_distrib) 
e96d5c42c4b0
Polymorphic treatment of binary arithmetic using axclasses
paulson
parents:
14377
diff
changeset

1125 

23482  1126 
lemma add_divide_eq_iff: 
1127 
"(z::'a::field) \<noteq> 0 \<Longrightarrow> x + y/z = (z*x + y)/z" 

1128 
by(simp add:add_divide_distrib nonzero_mult_divide_cancel_left) 

1129 

1130 
lemma divide_add_eq_iff: 

1131 
"(z::'a::field) \<noteq> 0 \<Longrightarrow> x/z + y = (x + z*y)/z" 

1132 
by(simp add:add_divide_distrib nonzero_mult_divide_cancel_left) 

1133 

1134 
lemma diff_divide_eq_iff: 

1135 
"(z::'a::field) \<noteq> 0 \<Longrightarrow> x  y/z = (z*x  y)/z" 

1136 
by(simp add:diff_divide_distrib nonzero_mult_divide_cancel_left) 

1137 

1138 
lemma divide_diff_eq_iff: 

1139 
"(z::'a::field) \<noteq> 0 \<Longrightarrow> x/z  y = (x  z*y)/z" 

1140 
by(simp add:diff_divide_distrib nonzero_mult_divide_cancel_left) 

1141 

1142 
lemma nonzero_eq_divide_eq: "c\<noteq>0 ==> ((a::'a::field) = b/c) = (a*c = b)" 

1143 
proof  

1144 
assume [simp]: "c\<noteq>0" 

23496  1145 
have "(a = b/c) = (a*c = (b/c)*c)" by simp 
1146 
also have "... = (a*c = b)" by (simp add: divide_inverse mult_assoc) 

23482  1147 
finally show ?thesis . 
1148 
qed 

1149 

1150 
lemma nonzero_divide_eq_eq: "c\<noteq>0 ==> (b/c = (a::'a::field)) = (b = a*c)" 

1151 
proof  

1152 
assume [simp]: "c\<noteq>0" 

23496  1153 
have "(b/c = a) = ((b/c)*c = a*c)" by simp 
1154 
also have "... = (b = a*c)" by (simp add: divide_inverse mult_assoc) 

23482  1155 
finally show ?thesis . 
1156 
qed 

1157 

1158 
lemma eq_divide_eq: 

1159 
"((a::'a::{field,division_by_zero}) = b/c) = (if c\<noteq>0 then a*c = b else a=0)" 

1160 
by (simp add: nonzero_eq_divide_eq) 

1161 

1162 
lemma divide_eq_eq: 

1163 
"(b/c = (a::'a::{field,division_by_zero})) = (if c\<noteq>0 then b = a*c else a=0)" 

1164 
by (force simp add: nonzero_divide_eq_eq) 

1165 

1166 
lemma divide_eq_imp: "(c::'a::{division_by_zero,field}) ~= 0 ==> 

1167 
b = a * c ==> b / c = a" 

1168 
by (subst divide_eq_eq, simp) 

1169 

1170 
lemma eq_divide_imp: "(c::'a::{division_by_zero,field}) ~= 0 ==> 

1171 
a * c = b ==> a = b / c" 

1172 
by (subst eq_divide_eq, simp) 

1173 

1174 

1175 
lemmas field_eq_simps = ring_simps 

1176 
(* pull / out*) 

1177 
add_divide_eq_iff divide_add_eq_iff 

1178 
diff_divide_eq_iff divide_diff_eq_iff 

1179 
(* multiply eqn *) 

1180 
nonzero_eq_divide_eq nonzero_divide_eq_eq 

1181 
(* is added later: 

1182 
times_divide_eq_left times_divide_eq_right 

1183 
*) 

1184 

1185 
text{*An example:*} 

1186 
lemma fixes a b c d e f :: "'a::field" 

1187 
shows "\<lbrakk>a\<noteq>b; c\<noteq>d; e\<noteq>f \<rbrakk> \<Longrightarrow> ((ab)*(cd)*(ef))/((cd)*(ef)*(ab)) = 1" 

1188 
apply(subgoal_tac "(cd)*(ef)*(ab) \<noteq> 0") 

1189 
apply(simp add:field_eq_simps) 

1190 
apply(simp) 

1191 
done 

1192 

1193 

16775
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

1194 
lemma diff_frac_eq: "(y::'a::field) ~= 0 ==> z ~= 0 ==> 
c1b87ef4a1c3
added lemmas to OrderedGroup.thy (reasoning about signs, absolute value, triangle inequalities)
avigad
parents:
16568
diff
changeset

1195 
x / y  w / z = (x * z  w * y) / (y * z)" 
23482  1196 
by (simp add:field_eq_simps times_divide_eq) 
1197 

1198 
lemma frac_eq_eq: "(y::'a::field) ~= 0 ==> z ~= 0 ==> 

1199 
(x / y = w / z) = (x * z = w * y)" 

1200 
by (simp add:field_eq_simps times_divide_eq) 

14293  1201 

23389  1202 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1203 
subsection {* Ordered Fields *} 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1204 

14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1205 
lemma positive_imp_inverse_positive: 
23482  1206 
assumes a_gt_0: "0 < a" shows "0 < inverse (a::'a::ordered_field)" 
1207 
proof  

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1208 
have "0 < a * inverse a" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1209 
by (simp add: a_gt_0 [THEN order_less_imp_not_eq2] zero_less_one) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1210 
thus "0 < inverse a" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1211 
by (simp add: a_gt_0 [THEN order_less_not_sym] zero_less_mult_iff) 
23482  1212 
qed 
14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1213 

14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1214 
lemma negative_imp_inverse_negative: 
23482  1215 
"a < 0 ==> inverse a < (0::'a::ordered_field)" 
1216 
by (insert positive_imp_inverse_positive [of "a"], 

1217 
simp add: nonzero_inverse_minus_eq order_less_imp_not_eq) 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1218 

5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1219 
lemma inverse_le_imp_le: 
23482  1220 
assumes invle: "inverse a \<le> inverse b" and apos: "0 < a" 
1221 
shows "b \<le> (a::'a::ordered_field)" 

1222 
proof (rule classical) 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1223 
assume "~ b \<le> a" 
23482  1224 
hence "a < b" by (simp add: linorder_not_le) 
1225 
hence bpos: "0 < b" by (blast intro: apos order_less_trans) 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1226 
hence "a * inverse a \<le> a * inverse b" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1227 
by (simp add: apos invle order_less_imp_le mult_left_mono) 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1228 
hence "(a * inverse a) * b \<le> (a * inverse b) * b" 
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1229 
by (simp add: bpos order_less_imp_le mult_right_mono) 
23482  1230 
thus "b \<le> a" by (simp add: mult_assoc apos bpos order_less_imp_not_eq2) 
1231 
qed 

14268
5cf13e80be0e
Removal of Hyperreal/ExtraThms2.ML, sending the material to the correct files.
paulson
parents:
14267
diff
changeset

1232 

14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1233 
lemma inverse_positive_imp_positive: 
23482  1234 
assumes inv_gt_0: "0 < inverse a" and nz: "a \<noteq> 0" 
1235 
shows "0 < (a::'a::ordered_field)" 

23389  1236 
proof  
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1237 
have "0 < inverse (inverse a)" 
23389  1238 
using inv_gt_0 by (rule positive_imp_inverse_positive) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1239 
thus "0 < a" 
23389  1240 
using nz by (simp add: nonzero_inverse_inverse_eq) 
1241 
qed 

14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1242 

ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1243 
lemma inverse_positive_iff_positive [simp]: 
23482  1244 
"(0 < inverse a) = (0 < (a::'a::{ordered_field,division_by_zero}))" 
21328  1245 
apply (cases "a = 0", simp) 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1246 
apply (blast intro: inverse_positive_imp_positive positive_imp_inverse_positive) 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1247 
done 
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1248 

ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1249 
lemma inverse_negative_imp_negative: 
23482  1250 
assumes inv_less_0: "inverse a < 0" and nz: "a \<noteq> 0" 
1251 
shows "a < (0::'a::ordered_field)" 

23389  1252 
proof  
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1253 
have "inverse (inverse a) < 0" 
23389  1254 
using inv_less_0 by (rule negative_imp_inverse_negative) 
23482  1255 
thus "a < 0" using nz by (simp add: nonzero_inverse_inverse_eq) 
23389  1256 
qed 
14277
ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1257 

ad66687ece6e
more field division lemmas transferred from Real to Ring_and_Field
paulson
parents:
14272
diff
changeset

1258 
lemma inverse_negative_iff_negative [simp]: 
23482  1259 
"(inverse a < 0) = (a < (0::'a::{ordered_field,division_by_zero}))" 