src/HOL/Real/PReal.thy
author huffman
Thu Sep 15 23:16:04 2005 +0200 (2005-09-15)
changeset 17428 8a2de150b5f1
parent 16775 c1b87ef4a1c3
child 18215 a28879118978
permissions -rw-r--r--
add header
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(*  Title       : PReal.thy
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    ID          : $Id$
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    Author      : Jacques D. Fleuriot
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    Copyright   : 1998  University of Cambridge
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    Description : The positive reals as Dedekind sections of positive
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         rationals. Fundamentals of Abstract Analysis [Gleason- p. 121]
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                  provides some of the definitions.
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*)
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header {* Positive real numbers *}
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theory PReal
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imports Rational
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begin
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text{*Could be generalized and moved to @{text Ring_and_Field}*}
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lemma add_eq_exists: "\<exists>x. a+x = (b::rat)"
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by (rule_tac x="b-a" in exI, simp)
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text{*As a special case, the sum of two positives is positive.  One of the
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premises could be weakened to the relation @{text "\<le>"}.*}
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lemma pos_add_strict: "[|0<a; b<c|] ==> b < a + (c::'a::ordered_semidom)"
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by (insert add_strict_mono [of 0 a b c], simp)
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lemma interval_empty_iff:
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     "({y::'a::ordered_field. x < y & y < z} = {}) = (~(x < z))"
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by (blast dest: dense intro: order_less_trans)
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constdefs
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  cut :: "rat set => bool"
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    "cut A == {} \<subset> A &
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              A < {r. 0 < r} &
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              (\<forall>y \<in> A. ((\<forall>z. 0<z & z < y --> z \<in> A) & (\<exists>u \<in> A. y < u)))"
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lemma cut_of_rat: 
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  assumes q: "0 < q" shows "cut {r::rat. 0 < r & r < q}"
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proof -
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  let ?A = "{r::rat. 0 < r & r < q}"
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  from q have pos: "?A < {r. 0 < r}" by force
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  have nonempty: "{} \<subset> ?A"
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  proof
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    show "{} \<subseteq> ?A" by simp
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    show "{} \<noteq> ?A"
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      by (force simp only: q eq_commute [of "{}"] interval_empty_iff)
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  qed
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  show ?thesis
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    by (simp add: cut_def pos nonempty,
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        blast dest: dense intro: order_less_trans)
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qed
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typedef preal = "{A. cut A}"
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  by (blast intro: cut_of_rat [OF zero_less_one])
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instance preal :: "{ord, plus, minus, times, inverse}" ..
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constdefs
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  preal_of_rat :: "rat => preal"
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     "preal_of_rat q == Abs_preal({x::rat. 0 < x & x < q})"
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  psup       :: "preal set => preal"
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    "psup(P)   == Abs_preal(\<Union>X \<in> P. Rep_preal(X))"
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  add_set :: "[rat set,rat set] => rat set"
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    "add_set A B == {w. \<exists>x \<in> A. \<exists>y \<in> B. w = x + y}"
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  diff_set :: "[rat set,rat set] => rat set"
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    "diff_set A B == {w. \<exists>x. 0 < w & 0 < x & x \<notin> B & x + w \<in> A}"
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  mult_set :: "[rat set,rat set] => rat set"
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    "mult_set A B == {w. \<exists>x \<in> A. \<exists>y \<in> B. w = x * y}"
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  inverse_set :: "rat set => rat set"
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    "inverse_set A == {x. \<exists>y. 0 < x & x < y & inverse y \<notin> A}"
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defs (overloaded)
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  preal_less_def:
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    "R < (S::preal) == Rep_preal R < Rep_preal S"
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  preal_le_def:
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    "R \<le> (S::preal) == Rep_preal R \<subseteq> Rep_preal S"
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  preal_add_def:
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    "R + S == Abs_preal (add_set (Rep_preal R) (Rep_preal S))"
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  preal_diff_def:
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    "R - S == Abs_preal (diff_set (Rep_preal R) (Rep_preal S))"
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  preal_mult_def:
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    "R * S == Abs_preal(mult_set (Rep_preal R) (Rep_preal S))"
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  preal_inverse_def:
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    "inverse R == Abs_preal(inverse_set (Rep_preal R))"
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text{*Reduces equality on abstractions to equality on representatives*}
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declare Abs_preal_inject [simp]
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lemma preal_nonempty: "A \<in> preal ==> \<exists>x\<in>A. 0 < x"
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by (unfold preal_def cut_def, blast)
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lemma preal_imp_psubset_positives: "A \<in> preal ==> A < {r. 0 < r}"
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by (force simp add: preal_def cut_def)
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lemma preal_exists_bound: "A \<in> preal ==> \<exists>x. 0 < x & x \<notin> A"
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by (drule preal_imp_psubset_positives, auto)
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lemma preal_exists_greater: "[| A \<in> preal; y \<in> A |] ==> \<exists>u \<in> A. y < u"
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by (unfold preal_def cut_def, blast)
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lemma mem_Rep_preal_Ex: "\<exists>x. x \<in> Rep_preal X"
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apply (insert Rep_preal [of X])
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apply (unfold preal_def cut_def, blast)
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done
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declare Abs_preal_inverse [simp]
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lemma preal_downwards_closed: "[| A \<in> preal; y \<in> A; 0 < z; z < y |] ==> z \<in> A"
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by (unfold preal_def cut_def, blast)
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text{*Relaxing the final premise*}
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lemma preal_downwards_closed':
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     "[| A \<in> preal; y \<in> A; 0 < z; z \<le> y |] ==> z \<in> A"
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apply (simp add: order_le_less)
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apply (blast intro: preal_downwards_closed)
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done
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lemma Rep_preal_exists_bound: "\<exists>x. 0 < x & x \<notin> Rep_preal X"
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apply (cut_tac x = X in Rep_preal)
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apply (drule preal_imp_psubset_positives)
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apply (auto simp add: psubset_def)
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done
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subsection{*@{term preal_of_prat}: the Injection from prat to preal*}
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lemma rat_less_set_mem_preal: "0 < y ==> {u::rat. 0 < u & u < y} \<in> preal"
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apply (auto simp add: preal_def cut_def intro: order_less_trans)
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apply (force simp only: eq_commute [of "{}"] interval_empty_iff)
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apply (blast dest: dense intro: order_less_trans)
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done
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lemma rat_subset_imp_le:
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     "[|{u::rat. 0 < u & u < x} \<subseteq> {u. 0 < u & u < y}; 0<x|] ==> x \<le> y"
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apply (simp add: linorder_not_less [symmetric])
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apply (blast dest: dense intro: order_less_trans)
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done
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lemma rat_set_eq_imp_eq:
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     "[|{u::rat. 0 < u & u < x} = {u. 0 < u & u < y};
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        0 < x; 0 < y|] ==> x = y"
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by (blast intro: rat_subset_imp_le order_antisym)
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subsection{*Theorems for Ordering*}
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text{*A positive fraction not in a positive real is an upper bound.
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 Gleason p. 122 - Remark (1)*}
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lemma not_in_preal_ub:
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     assumes A: "A \<in> preal"
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         and notx: "x \<notin> A"
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         and y: "y \<in> A"
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         and pos: "0 < x"
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        shows "y < x"
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proof (cases rule: linorder_cases)
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  assume "x<y"
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  with notx show ?thesis
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    by (simp add:  preal_downwards_closed [OF A y] pos)
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next
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  assume "x=y"
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  with notx and y show ?thesis by simp
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next
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  assume "y<x"
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  thus ?thesis by assumption
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qed
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lemmas not_in_Rep_preal_ub = not_in_preal_ub [OF Rep_preal]
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subsection{*The @{text "\<le>"} Ordering*}
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lemma preal_le_refl: "w \<le> (w::preal)"
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by (simp add: preal_le_def)
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lemma preal_le_trans: "[| i \<le> j; j \<le> k |] ==> i \<le> (k::preal)"
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by (force simp add: preal_le_def)
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lemma preal_le_anti_sym: "[| z \<le> w; w \<le> z |] ==> z = (w::preal)"
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apply (simp add: preal_le_def)
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apply (rule Rep_preal_inject [THEN iffD1], blast)
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done
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(* Axiom 'order_less_le' of class 'order': *)
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lemma preal_less_le: "((w::preal) < z) = (w \<le> z & w \<noteq> z)"
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by (simp add: preal_le_def preal_less_def Rep_preal_inject psubset_def)
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instance preal :: order
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  by intro_classes
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    (assumption |
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      rule preal_le_refl preal_le_trans preal_le_anti_sym preal_less_le)+
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lemma preal_imp_pos: "[|A \<in> preal; r \<in> A|] ==> 0 < r"
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by (insert preal_imp_psubset_positives, blast)
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lemma preal_le_linear: "x <= y | y <= (x::preal)"
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apply (auto simp add: preal_le_def)
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apply (rule ccontr)
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apply (blast dest: not_in_Rep_preal_ub intro: preal_imp_pos [OF Rep_preal]
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             elim: order_less_asym)
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done
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instance preal :: linorder
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  by intro_classes (rule preal_le_linear)
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subsection{*Properties of Addition*}
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lemma preal_add_commute: "(x::preal) + y = y + x"
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apply (unfold preal_add_def add_set_def)
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apply (rule_tac f = Abs_preal in arg_cong)
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apply (force simp add: add_commute)
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done
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text{*Lemmas for proving that addition of two positive reals gives
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 a positive real*}
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lemma empty_psubset_nonempty: "a \<in> A ==> {} \<subset> A"
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by blast
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text{*Part 1 of Dedekind sections definition*}
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lemma add_set_not_empty:
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     "[|A \<in> preal; B \<in> preal|] ==> {} \<subset> add_set A B"
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apply (insert preal_nonempty [of A] preal_nonempty [of B]) 
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apply (auto simp add: add_set_def)
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done
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text{*Part 2 of Dedekind sections definition.  A structured version of
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this proof is @{text preal_not_mem_mult_set_Ex} below.*}
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lemma preal_not_mem_add_set_Ex:
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     "[|A \<in> preal; B \<in> preal|] ==> \<exists>q. 0 < q & q \<notin> add_set A B"
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apply (insert preal_exists_bound [of A] preal_exists_bound [of B], auto) 
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apply (rule_tac x = "x+xa" in exI)
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apply (simp add: add_set_def, clarify)
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apply (drule not_in_preal_ub, assumption+)+
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apply (force dest: add_strict_mono)
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done
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lemma add_set_not_rat_set:
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   assumes A: "A \<in> preal" 
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       and B: "B \<in> preal"
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     shows "add_set A B < {r. 0 < r}"
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proof
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  from preal_imp_pos [OF A] preal_imp_pos [OF B]
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  show "add_set A B \<subseteq> {r. 0 < r}" by (force simp add: add_set_def) 
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next
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  show "add_set A B \<noteq> {r. 0 < r}"
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    by (insert preal_not_mem_add_set_Ex [OF A B], blast) 
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qed
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text{*Part 3 of Dedekind sections definition*}
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lemma add_set_lemma3:
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     "[|A \<in> preal; B \<in> preal; u \<in> add_set A B; 0 < z; z < u|] 
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      ==> z \<in> add_set A B"
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proof (unfold add_set_def, clarify)
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  fix x::rat and y::rat
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  assume A: "A \<in> preal" 
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     and B: "B \<in> preal"
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     and [simp]: "0 < z"
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     and zless: "z < x + y"
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     and x:  "x \<in> A"
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     and y:  "y \<in> B"
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  have xpos [simp]: "0<x" by (rule preal_imp_pos [OF A x])
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  have ypos [simp]: "0<y" by (rule preal_imp_pos [OF B y])
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  have xypos [simp]: "0 < x+y" by (simp add: pos_add_strict)
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  let ?f = "z/(x+y)"
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  have fless: "?f < 1" by (simp add: zless pos_divide_less_eq)
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  show "\<exists>x' \<in> A. \<exists>y'\<in>B. z = x' + y'"
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  proof
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    show "\<exists>y' \<in> B. z = x*?f + y'"
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    proof
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      show "z = x*?f + y*?f"
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	by (simp add: left_distrib [symmetric] divide_inverse mult_ac
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		      order_less_imp_not_eq2)
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    next
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      show "y * ?f \<in> B"
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      proof (rule preal_downwards_closed [OF B y])
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        show "0 < y * ?f"
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          by (simp add: divide_inverse zero_less_mult_iff)
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      next
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        show "y * ?f < y"
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          by (insert mult_strict_left_mono [OF fless ypos], simp)
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      qed
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    qed
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  next
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    show "x * ?f \<in> A"
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    proof (rule preal_downwards_closed [OF A x])
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      show "0 < x * ?f"
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	by (simp add: divide_inverse zero_less_mult_iff)
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    next
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      show "x * ?f < x"
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	by (insert mult_strict_left_mono [OF fless xpos], simp)
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    qed
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  qed
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qed
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text{*Part 4 of Dedekind sections definition*}
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lemma add_set_lemma4:
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     "[|A \<in> preal; B \<in> preal; y \<in> add_set A B|] ==> \<exists>u \<in> add_set A B. y < u"
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apply (auto simp add: add_set_def)
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apply (frule preal_exists_greater [of A], auto) 
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apply (rule_tac x="u + y" in exI)
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apply (auto intro: add_strict_left_mono)
paulson@14335
   320
done
paulson@14335
   321
paulson@14365
   322
lemma mem_add_set:
paulson@14365
   323
     "[|A \<in> preal; B \<in> preal|] ==> add_set A B \<in> preal"
paulson@14365
   324
apply (simp (no_asm_simp) add: preal_def cut_def)
paulson@14365
   325
apply (blast intro!: add_set_not_empty add_set_not_rat_set
paulson@14365
   326
                     add_set_lemma3 add_set_lemma4)
paulson@14335
   327
done
paulson@14335
   328
paulson@14335
   329
lemma preal_add_assoc: "((x::preal) + y) + z = x + (y + z)"
paulson@14365
   330
apply (simp add: preal_add_def mem_add_set Rep_preal)
paulson@14365
   331
apply (force simp add: add_set_def add_ac)
paulson@14335
   332
done
paulson@14335
   333
paulson@14335
   334
lemma preal_add_left_commute: "x + (y + z) = y + ((x + z)::preal)"
paulson@14335
   335
  apply (rule mk_left_commute [of "op +"])
paulson@14335
   336
  apply (rule preal_add_assoc)
paulson@14335
   337
  apply (rule preal_add_commute)
paulson@14335
   338
  done
paulson@14335
   339
paulson@14365
   340
text{* Positive Real addition is an AC operator *}
paulson@14335
   341
lemmas preal_add_ac = preal_add_assoc preal_add_commute preal_add_left_commute
paulson@14335
   342
paulson@14335
   343
paulson@14335
   344
subsection{*Properties of Multiplication*}
paulson@14335
   345
paulson@14335
   346
text{*Proofs essentially same as for addition*}
paulson@14335
   347
paulson@14335
   348
lemma preal_mult_commute: "(x::preal) * y = y * x"
paulson@14365
   349
apply (unfold preal_mult_def mult_set_def)
paulson@14335
   350
apply (rule_tac f = Abs_preal in arg_cong)
paulson@14365
   351
apply (force simp add: mult_commute)
paulson@14335
   352
done
paulson@14335
   353
nipkow@15055
   354
text{*Multiplication of two positive reals gives a positive real.*}
paulson@14335
   355
paulson@14335
   356
text{*Lemmas for proving positive reals multiplication set in @{typ preal}*}
paulson@14335
   357
paulson@14335
   358
text{*Part 1 of Dedekind sections definition*}
paulson@14365
   359
lemma mult_set_not_empty:
paulson@14365
   360
     "[|A \<in> preal; B \<in> preal|] ==> {} \<subset> mult_set A B"
paulson@14365
   361
apply (insert preal_nonempty [of A] preal_nonempty [of B]) 
paulson@14365
   362
apply (auto simp add: mult_set_def)
paulson@14335
   363
done
paulson@14335
   364
paulson@14335
   365
text{*Part 2 of Dedekind sections definition*}
paulson@14335
   366
lemma preal_not_mem_mult_set_Ex:
paulson@14365
   367
   assumes A: "A \<in> preal" 
paulson@14365
   368
       and B: "B \<in> preal"
paulson@14365
   369
     shows "\<exists>q. 0 < q & q \<notin> mult_set A B"
paulson@14365
   370
proof -
paulson@14365
   371
  from preal_exists_bound [OF A]
paulson@14365
   372
  obtain x where [simp]: "0 < x" "x \<notin> A" by blast
paulson@14365
   373
  from preal_exists_bound [OF B]
paulson@14365
   374
  obtain y where [simp]: "0 < y" "y \<notin> B" by blast
paulson@14365
   375
  show ?thesis
paulson@14365
   376
  proof (intro exI conjI)
avigad@16775
   377
    show "0 < x*y" by (simp add: mult_pos_pos)
paulson@14365
   378
    show "x * y \<notin> mult_set A B"
paulson@14377
   379
    proof -
paulson@14377
   380
      { fix u::rat and v::rat
kleing@14550
   381
	      assume "u \<in> A" and "v \<in> B" and "x*y = u*v"
kleing@14550
   382
	      moreover
kleing@14550
   383
	      with prems have "u<x" and "v<y" by (blast dest: not_in_preal_ub)+
kleing@14550
   384
	      moreover
kleing@14550
   385
	      with prems have "0\<le>v"
kleing@14550
   386
	        by (blast intro: preal_imp_pos [OF B]  order_less_imp_le prems)
kleing@14550
   387
	      moreover
kleing@14550
   388
        from calculation
kleing@14550
   389
	      have "u*v < x*y" by (blast intro: mult_strict_mono prems)
kleing@14550
   390
	      ultimately have False by force }
paulson@14377
   391
      thus ?thesis by (auto simp add: mult_set_def)
paulson@14365
   392
    qed
paulson@14365
   393
  qed
paulson@14365
   394
qed
paulson@14335
   395
paulson@14365
   396
lemma mult_set_not_rat_set:
paulson@14365
   397
   assumes A: "A \<in> preal" 
paulson@14365
   398
       and B: "B \<in> preal"
paulson@14365
   399
     shows "mult_set A B < {r. 0 < r}"
paulson@14365
   400
proof
paulson@14365
   401
  show "mult_set A B \<subseteq> {r. 0 < r}"
paulson@14365
   402
    by (force simp add: mult_set_def
avigad@16775
   403
              intro: preal_imp_pos [OF A] preal_imp_pos [OF B] mult_pos_pos)
paulson@14365
   404
next
paulson@14365
   405
  show "mult_set A B \<noteq> {r. 0 < r}"
paulson@14365
   406
    by (insert preal_not_mem_mult_set_Ex [OF A B], blast)
paulson@14365
   407
qed
paulson@14365
   408
paulson@14365
   409
paulson@14335
   410
paulson@14335
   411
text{*Part 3 of Dedekind sections definition*}
paulson@14365
   412
lemma mult_set_lemma3:
paulson@14365
   413
     "[|A \<in> preal; B \<in> preal; u \<in> mult_set A B; 0 < z; z < u|] 
paulson@14365
   414
      ==> z \<in> mult_set A B"
paulson@14365
   415
proof (unfold mult_set_def, clarify)
paulson@14365
   416
  fix x::rat and y::rat
paulson@14365
   417
  assume A: "A \<in> preal" 
paulson@14365
   418
     and B: "B \<in> preal"
paulson@14365
   419
     and [simp]: "0 < z"
paulson@14365
   420
     and zless: "z < x * y"
paulson@14365
   421
     and x:  "x \<in> A"
paulson@14365
   422
     and y:  "y \<in> B"
paulson@14365
   423
  have [simp]: "0<y" by (rule preal_imp_pos [OF B y])
paulson@14365
   424
  show "\<exists>x' \<in> A. \<exists>y' \<in> B. z = x' * y'"
paulson@14365
   425
  proof
paulson@14365
   426
    show "\<exists>y'\<in>B. z = (z/y) * y'"
paulson@14365
   427
    proof
paulson@14365
   428
      show "z = (z/y)*y"
paulson@14430
   429
	by (simp add: divide_inverse mult_commute [of y] mult_assoc
paulson@14365
   430
		      order_less_imp_not_eq2)
paulson@14365
   431
      show "y \<in> B" .
paulson@14365
   432
    qed
paulson@14365
   433
  next
paulson@14365
   434
    show "z/y \<in> A"
paulson@14365
   435
    proof (rule preal_downwards_closed [OF A x])
paulson@14365
   436
      show "0 < z/y"
paulson@14365
   437
	by (simp add: zero_less_divide_iff)
paulson@14365
   438
      show "z/y < x" by (simp add: pos_divide_less_eq zless)
paulson@14365
   439
    qed
paulson@14365
   440
  qed
paulson@14365
   441
qed
paulson@14365
   442
paulson@14365
   443
text{*Part 4 of Dedekind sections definition*}
paulson@14365
   444
lemma mult_set_lemma4:
paulson@14365
   445
     "[|A \<in> preal; B \<in> preal; y \<in> mult_set A B|] ==> \<exists>u \<in> mult_set A B. y < u"
paulson@14365
   446
apply (auto simp add: mult_set_def)
paulson@14365
   447
apply (frule preal_exists_greater [of A], auto) 
paulson@14365
   448
apply (rule_tac x="u * y" in exI)
paulson@14365
   449
apply (auto intro: preal_imp_pos [of A] preal_imp_pos [of B] 
paulson@14365
   450
                   mult_strict_right_mono)
paulson@14335
   451
done
paulson@14335
   452
paulson@14335
   453
paulson@14365
   454
lemma mem_mult_set:
paulson@14365
   455
     "[|A \<in> preal; B \<in> preal|] ==> mult_set A B \<in> preal"
paulson@14365
   456
apply (simp (no_asm_simp) add: preal_def cut_def)
paulson@14365
   457
apply (blast intro!: mult_set_not_empty mult_set_not_rat_set
paulson@14365
   458
                     mult_set_lemma3 mult_set_lemma4)
paulson@14335
   459
done
paulson@14335
   460
paulson@14335
   461
lemma preal_mult_assoc: "((x::preal) * y) * z = x * (y * z)"
paulson@14365
   462
apply (simp add: preal_mult_def mem_mult_set Rep_preal)
paulson@14365
   463
apply (force simp add: mult_set_def mult_ac)
paulson@14335
   464
done
paulson@14335
   465
paulson@14335
   466
lemma preal_mult_left_commute: "x * (y * z) = y * ((x * z)::preal)"
paulson@14335
   467
  apply (rule mk_left_commute [of "op *"])
paulson@14335
   468
  apply (rule preal_mult_assoc)
paulson@14335
   469
  apply (rule preal_mult_commute)
paulson@14335
   470
  done
paulson@14335
   471
paulson@14365
   472
paulson@14365
   473
text{* Positive Real multiplication is an AC operator *}
paulson@14335
   474
lemmas preal_mult_ac =
paulson@14335
   475
       preal_mult_assoc preal_mult_commute preal_mult_left_commute
paulson@14335
   476
paulson@14365
   477
paulson@14365
   478
text{* Positive real 1 is the multiplicative identity element *}
paulson@14365
   479
paulson@14365
   480
lemma rat_mem_preal: "0 < q ==> {r::rat. 0 < r & r < q} \<in> preal"
paulson@14365
   481
by (simp add: preal_def cut_of_rat)
paulson@14335
   482
paulson@14365
   483
lemma preal_mult_1: "(preal_of_rat 1) * z = z"
paulson@14365
   484
proof (induct z)
paulson@14365
   485
  fix A :: "rat set"
paulson@14365
   486
  assume A: "A \<in> preal"
paulson@14365
   487
  have "{w. \<exists>u. 0 < u \<and> u < 1 & (\<exists>v \<in> A. w = u * v)} = A" (is "?lhs = A")
paulson@14365
   488
  proof
paulson@14365
   489
    show "?lhs \<subseteq> A"
paulson@14365
   490
    proof clarify
paulson@14365
   491
      fix x::rat and u::rat and v::rat
paulson@14365
   492
      assume upos: "0<u" and "u<1" and v: "v \<in> A"
paulson@14365
   493
      have vpos: "0<v" by (rule preal_imp_pos [OF A v])
paulson@14365
   494
      hence "u*v < 1*v" by (simp only: mult_strict_right_mono prems)
paulson@14365
   495
      thus "u * v \<in> A"
avigad@16775
   496
        by (force intro: preal_downwards_closed [OF A v] mult_pos_pos 
avigad@16775
   497
          upos vpos)
paulson@14365
   498
    qed
paulson@14365
   499
  next
paulson@14365
   500
    show "A \<subseteq> ?lhs"
paulson@14365
   501
    proof clarify
paulson@14365
   502
      fix x::rat
paulson@14365
   503
      assume x: "x \<in> A"
paulson@14365
   504
      have xpos: "0<x" by (rule preal_imp_pos [OF A x])
paulson@14365
   505
      from preal_exists_greater [OF A x]
paulson@14365
   506
      obtain v where v: "v \<in> A" and xlessv: "x < v" ..
paulson@14365
   507
      have vpos: "0<v" by (rule preal_imp_pos [OF A v])
paulson@14365
   508
      show "\<exists>u. 0 < u \<and> u < 1 \<and> (\<exists>v\<in>A. x = u * v)"
paulson@14365
   509
      proof (intro exI conjI)
paulson@14365
   510
        show "0 < x/v"
paulson@14365
   511
          by (simp add: zero_less_divide_iff xpos vpos)
paulson@14365
   512
	show "x / v < 1"
paulson@14365
   513
          by (simp add: pos_divide_less_eq vpos xlessv)
paulson@14365
   514
        show "\<exists>v'\<in>A. x = (x / v) * v'"
paulson@14365
   515
        proof
paulson@14365
   516
          show "x = (x/v)*v"
paulson@14430
   517
	    by (simp add: divide_inverse mult_assoc vpos
paulson@14365
   518
                          order_less_imp_not_eq2)
paulson@14365
   519
          show "v \<in> A" .
paulson@14365
   520
        qed
paulson@14365
   521
      qed
paulson@14365
   522
    qed
paulson@14365
   523
  qed
paulson@14365
   524
  thus "preal_of_rat 1 * Abs_preal A = Abs_preal A"
paulson@14365
   525
    by (simp add: preal_of_rat_def preal_mult_def mult_set_def 
paulson@14365
   526
                  rat_mem_preal A)
paulson@14365
   527
qed
paulson@14365
   528
paulson@14365
   529
paulson@14365
   530
lemma preal_mult_1_right: "z * (preal_of_rat 1) = z"
paulson@14335
   531
apply (rule preal_mult_commute [THEN subst])
paulson@14335
   532
apply (rule preal_mult_1)
paulson@14335
   533
done
paulson@14335
   534
paulson@14335
   535
paulson@14335
   536
subsection{*Distribution of Multiplication across Addition*}
paulson@14335
   537
paulson@14335
   538
lemma mem_Rep_preal_add_iff:
paulson@14365
   539
      "(z \<in> Rep_preal(R+S)) = (\<exists>x \<in> Rep_preal R. \<exists>y \<in> Rep_preal S. z = x + y)"
paulson@14365
   540
apply (simp add: preal_add_def mem_add_set Rep_preal)
paulson@14365
   541
apply (simp add: add_set_def) 
paulson@14335
   542
done
paulson@14335
   543
paulson@14335
   544
lemma mem_Rep_preal_mult_iff:
paulson@14365
   545
      "(z \<in> Rep_preal(R*S)) = (\<exists>x \<in> Rep_preal R. \<exists>y \<in> Rep_preal S. z = x * y)"
paulson@14365
   546
apply (simp add: preal_mult_def mem_mult_set Rep_preal)
paulson@14365
   547
apply (simp add: mult_set_def) 
paulson@14365
   548
done
paulson@14335
   549
paulson@14365
   550
lemma distrib_subset1:
paulson@14365
   551
     "Rep_preal (w * (x + y)) \<subseteq> Rep_preal (w * x + w * y)"
paulson@14365
   552
apply (auto simp add: Bex_def mem_Rep_preal_add_iff mem_Rep_preal_mult_iff)
paulson@14365
   553
apply (force simp add: right_distrib)
paulson@14335
   554
done
paulson@14335
   555
paulson@14365
   556
lemma linorder_le_cases [case_names le ge]:
paulson@14365
   557
    "((x::'a::linorder) <= y ==> P) ==> (y <= x ==> P) ==> P"
paulson@14365
   558
  apply (insert linorder_linear, blast)
paulson@14365
   559
  done
paulson@14335
   560
paulson@14365
   561
lemma preal_add_mult_distrib_mean:
paulson@14365
   562
  assumes a: "a \<in> Rep_preal w"
paulson@14365
   563
      and b: "b \<in> Rep_preal w"
paulson@14365
   564
      and d: "d \<in> Rep_preal x"
paulson@14365
   565
      and e: "e \<in> Rep_preal y"
paulson@14365
   566
     shows "\<exists>c \<in> Rep_preal w. a * d + b * e = c * (d + e)"
paulson@14365
   567
proof
paulson@14365
   568
  let ?c = "(a*d + b*e)/(d+e)"
paulson@14365
   569
  have [simp]: "0<a" "0<b" "0<d" "0<e" "0<d+e"
paulson@14365
   570
    by (blast intro: preal_imp_pos [OF Rep_preal] a b d e pos_add_strict)+
paulson@14365
   571
  have cpos: "0 < ?c"
paulson@14365
   572
    by (simp add: zero_less_divide_iff zero_less_mult_iff pos_add_strict)
paulson@14365
   573
  show "a * d + b * e = ?c * (d + e)"
paulson@14430
   574
    by (simp add: divide_inverse mult_assoc order_less_imp_not_eq2)
paulson@14365
   575
  show "?c \<in> Rep_preal w"
paulson@14365
   576
    proof (cases rule: linorder_le_cases)
paulson@14365
   577
      assume "a \<le> b"
paulson@14365
   578
      hence "?c \<le> b"
paulson@14365
   579
	by (simp add: pos_divide_le_eq right_distrib mult_right_mono
paulson@14365
   580
                      order_less_imp_le)
paulson@14365
   581
      thus ?thesis by (rule preal_downwards_closed' [OF Rep_preal b cpos])
paulson@14365
   582
    next
paulson@14365
   583
      assume "b \<le> a"
paulson@14365
   584
      hence "?c \<le> a"
paulson@14365
   585
	by (simp add: pos_divide_le_eq right_distrib mult_right_mono
paulson@14365
   586
                      order_less_imp_le)
paulson@14365
   587
      thus ?thesis by (rule preal_downwards_closed' [OF Rep_preal a cpos])
paulson@14365
   588
    qed
paulson@14365
   589
  qed
paulson@14365
   590
paulson@14365
   591
lemma distrib_subset2:
paulson@14365
   592
     "Rep_preal (w * x + w * y) \<subseteq> Rep_preal (w * (x + y))"
paulson@14365
   593
apply (auto simp add: Bex_def mem_Rep_preal_add_iff mem_Rep_preal_mult_iff)
paulson@14365
   594
apply (drule_tac w=w and x=x and y=y in preal_add_mult_distrib_mean, auto)
paulson@14335
   595
done
paulson@14335
   596
paulson@14365
   597
lemma preal_add_mult_distrib2: "(w * ((x::preal) + y)) = (w * x) + (w * y)"
paulson@15413
   598
apply (rule Rep_preal_inject [THEN iffD1])
paulson@14365
   599
apply (rule equalityI [OF distrib_subset1 distrib_subset2])
paulson@14335
   600
done
paulson@14335
   601
paulson@14365
   602
lemma preal_add_mult_distrib: "(((x::preal) + y) * w) = (x * w) + (y * w)"
paulson@14365
   603
by (simp add: preal_mult_commute preal_add_mult_distrib2)
paulson@14365
   604
paulson@14335
   605
paulson@14335
   606
subsection{*Existence of Inverse, a Positive Real*}
paulson@14335
   607
paulson@14365
   608
lemma mem_inv_set_ex:
paulson@14365
   609
  assumes A: "A \<in> preal" shows "\<exists>x y. 0 < x & x < y & inverse y \<notin> A"
paulson@14365
   610
proof -
paulson@14365
   611
  from preal_exists_bound [OF A]
paulson@14365
   612
  obtain x where [simp]: "0<x" "x \<notin> A" by blast
paulson@14365
   613
  show ?thesis
paulson@14365
   614
  proof (intro exI conjI)
paulson@14365
   615
    show "0 < inverse (x+1)"
paulson@14365
   616
      by (simp add: order_less_trans [OF _ less_add_one]) 
paulson@14365
   617
    show "inverse(x+1) < inverse x"
paulson@14365
   618
      by (simp add: less_imp_inverse_less less_add_one)
paulson@14365
   619
    show "inverse (inverse x) \<notin> A"
paulson@14365
   620
      by (simp add: order_less_imp_not_eq2)
paulson@14365
   621
  qed
paulson@14365
   622
qed
paulson@14335
   623
paulson@14335
   624
text{*Part 1 of Dedekind sections definition*}
paulson@14365
   625
lemma inverse_set_not_empty:
paulson@14365
   626
     "A \<in> preal ==> {} \<subset> inverse_set A"
paulson@14365
   627
apply (insert mem_inv_set_ex [of A])
paulson@14365
   628
apply (auto simp add: inverse_set_def)
paulson@14335
   629
done
paulson@14335
   630
paulson@14335
   631
text{*Part 2 of Dedekind sections definition*}
paulson@14335
   632
paulson@14365
   633
lemma preal_not_mem_inverse_set_Ex:
paulson@14365
   634
   assumes A: "A \<in> preal"  shows "\<exists>q. 0 < q & q \<notin> inverse_set A"
paulson@14365
   635
proof -
paulson@14365
   636
  from preal_nonempty [OF A]
paulson@14365
   637
  obtain x where x: "x \<in> A" and  xpos [simp]: "0<x" ..
paulson@14365
   638
  show ?thesis
paulson@14365
   639
  proof (intro exI conjI)
paulson@14365
   640
    show "0 < inverse x" by simp
paulson@14365
   641
    show "inverse x \<notin> inverse_set A"
paulson@14377
   642
    proof -
paulson@14377
   643
      { fix y::rat 
paulson@14377
   644
	assume ygt: "inverse x < y"
paulson@14377
   645
	have [simp]: "0 < y" by (simp add: order_less_trans [OF _ ygt])
paulson@14377
   646
	have iyless: "inverse y < x" 
paulson@14377
   647
	  by (simp add: inverse_less_imp_less [of x] ygt)
paulson@14377
   648
	have "inverse y \<in> A"
paulson@14377
   649
	  by (simp add: preal_downwards_closed [OF A x] iyless)}
paulson@14377
   650
     thus ?thesis by (auto simp add: inverse_set_def)
paulson@14365
   651
    qed
paulson@14365
   652
  qed
paulson@14365
   653
qed
paulson@14335
   654
paulson@14365
   655
lemma inverse_set_not_rat_set:
paulson@14365
   656
   assumes A: "A \<in> preal"  shows "inverse_set A < {r. 0 < r}"
paulson@14365
   657
proof
paulson@14365
   658
  show "inverse_set A \<subseteq> {r. 0 < r}"  by (force simp add: inverse_set_def)
paulson@14365
   659
next
paulson@14365
   660
  show "inverse_set A \<noteq> {r. 0 < r}"
paulson@14365
   661
    by (insert preal_not_mem_inverse_set_Ex [OF A], blast)
paulson@14365
   662
qed
paulson@14335
   663
paulson@14335
   664
text{*Part 3 of Dedekind sections definition*}
paulson@14365
   665
lemma inverse_set_lemma3:
paulson@14365
   666
     "[|A \<in> preal; u \<in> inverse_set A; 0 < z; z < u|] 
paulson@14365
   667
      ==> z \<in> inverse_set A"
paulson@14365
   668
apply (auto simp add: inverse_set_def)
paulson@14365
   669
apply (auto intro: order_less_trans)
paulson@14335
   670
done
paulson@14335
   671
paulson@14365
   672
text{*Part 4 of Dedekind sections definition*}
paulson@14365
   673
lemma inverse_set_lemma4:
paulson@14365
   674
     "[|A \<in> preal; y \<in> inverse_set A|] ==> \<exists>u \<in> inverse_set A. y < u"
paulson@14365
   675
apply (auto simp add: inverse_set_def)
paulson@14365
   676
apply (drule dense [of y]) 
paulson@14365
   677
apply (blast intro: order_less_trans)
paulson@14335
   678
done
paulson@14335
   679
paulson@14365
   680
paulson@14365
   681
lemma mem_inverse_set:
paulson@14365
   682
     "A \<in> preal ==> inverse_set A \<in> preal"
paulson@14365
   683
apply (simp (no_asm_simp) add: preal_def cut_def)
paulson@14365
   684
apply (blast intro!: inverse_set_not_empty inverse_set_not_rat_set
paulson@14365
   685
                     inverse_set_lemma3 inverse_set_lemma4)
paulson@14335
   686
done
paulson@14335
   687
paulson@14365
   688
paulson@14335
   689
subsection{*Gleason's Lemma 9-3.4, page 122*}
paulson@14335
   690
paulson@14365
   691
lemma Gleason9_34_exists:
paulson@14365
   692
  assumes A: "A \<in> preal"
paulson@14369
   693
      and "\<forall>x\<in>A. x + u \<in> A"
paulson@14369
   694
      and "0 \<le> z"
paulson@14378
   695
     shows "\<exists>b\<in>A. b + (of_int z) * u \<in> A"
paulson@14369
   696
proof (cases z rule: int_cases)
paulson@14369
   697
  case (nonneg n)
paulson@14365
   698
  show ?thesis
paulson@14365
   699
  proof (simp add: prems, induct n)
paulson@14365
   700
    case 0
paulson@14365
   701
      from preal_nonempty [OF A]
paulson@14365
   702
      show ?case  by force 
paulson@14365
   703
    case (Suc k)
paulson@15013
   704
      from this obtain b where "b \<in> A" "b + of_nat k * u \<in> A" ..
paulson@14378
   705
      hence "b + of_int (int k)*u + u \<in> A" by (simp add: prems)
paulson@14365
   706
      thus ?case by (force simp add: left_distrib add_ac prems) 
paulson@14365
   707
  qed
paulson@14365
   708
next
paulson@14369
   709
  case (neg n)
paulson@14369
   710
  with prems show ?thesis by simp
paulson@14365
   711
qed
paulson@14365
   712
paulson@14365
   713
lemma Gleason9_34_contra:
paulson@14365
   714
  assumes A: "A \<in> preal"
paulson@14365
   715
    shows "[|\<forall>x\<in>A. x + u \<in> A; 0 < u; 0 < y; y \<notin> A|] ==> False"
paulson@14365
   716
proof (induct u, induct y)
paulson@14365
   717
  fix a::int and b::int
paulson@14365
   718
  fix c::int and d::int
paulson@14365
   719
  assume bpos [simp]: "0 < b"
paulson@14365
   720
     and dpos [simp]: "0 < d"
paulson@14365
   721
     and closed: "\<forall>x\<in>A. x + (Fract c d) \<in> A"
paulson@14365
   722
     and upos: "0 < Fract c d"
paulson@14365
   723
     and ypos: "0 < Fract a b"
paulson@14365
   724
     and notin: "Fract a b \<notin> A"
paulson@14365
   725
  have cpos [simp]: "0 < c" 
paulson@14365
   726
    by (simp add: zero_less_Fract_iff [OF dpos, symmetric] upos) 
paulson@14365
   727
  have apos [simp]: "0 < a" 
paulson@14365
   728
    by (simp add: zero_less_Fract_iff [OF bpos, symmetric] ypos) 
paulson@14365
   729
  let ?k = "a*d"
paulson@14378
   730
  have frle: "Fract a b \<le> Fract ?k 1 * (Fract c d)" 
paulson@14365
   731
  proof -
paulson@14365
   732
    have "?thesis = ((a * d * b * d) \<le> c * b * (a * d * b * d))"
paulson@14378
   733
      by (simp add: mult_rat le_rat order_less_imp_not_eq2 mult_ac) 
paulson@14365
   734
    moreover
paulson@14365
   735
    have "(1 * (a * d * b * d)) \<le> c * b * (a * d * b * d)"
paulson@14365
   736
      by (rule mult_mono, 
paulson@14365
   737
          simp_all add: int_one_le_iff_zero_less zero_less_mult_iff 
paulson@14365
   738
                        order_less_imp_le)
paulson@14365
   739
    ultimately
paulson@14365
   740
    show ?thesis by simp
paulson@14365
   741
  qed
paulson@14365
   742
  have k: "0 \<le> ?k" by (simp add: order_less_imp_le zero_less_mult_iff)  
paulson@14365
   743
  from Gleason9_34_exists [OF A closed k]
paulson@14365
   744
  obtain z where z: "z \<in> A" 
paulson@14378
   745
             and mem: "z + of_int ?k * Fract c d \<in> A" ..
paulson@14378
   746
  have less: "z + of_int ?k * Fract c d < Fract a b"
paulson@14365
   747
    by (rule not_in_preal_ub [OF A notin mem ypos])
paulson@14365
   748
  have "0<z" by (rule preal_imp_pos [OF A z])
paulson@14378
   749
  with frle and less show False by (simp add: Fract_of_int_eq) 
paulson@14365
   750
qed
paulson@14335
   751
paulson@14335
   752
paulson@14365
   753
lemma Gleason9_34:
paulson@14365
   754
  assumes A: "A \<in> preal"
paulson@14365
   755
      and upos: "0 < u"
paulson@14365
   756
    shows "\<exists>r \<in> A. r + u \<notin> A"
paulson@14365
   757
proof (rule ccontr, simp)
paulson@14365
   758
  assume closed: "\<forall>r\<in>A. r + u \<in> A"
paulson@14365
   759
  from preal_exists_bound [OF A]
paulson@14365
   760
  obtain y where y: "y \<notin> A" and ypos: "0 < y" by blast
paulson@14365
   761
  show False
paulson@14365
   762
    by (rule Gleason9_34_contra [OF A closed upos ypos y])
paulson@14365
   763
qed
paulson@14365
   764
paulson@14335
   765
paulson@14335
   766
paulson@14335
   767
subsection{*Gleason's Lemma 9-3.6*}
paulson@14335
   768
paulson@14365
   769
lemma lemma_gleason9_36:
paulson@14365
   770
  assumes A: "A \<in> preal"
paulson@14365
   771
      and x: "1 < x"
paulson@14365
   772
    shows "\<exists>r \<in> A. r*x \<notin> A"
paulson@14365
   773
proof -
paulson@14365
   774
  from preal_nonempty [OF A]
paulson@14365
   775
  obtain y where y: "y \<in> A" and  ypos: "0<y" ..
paulson@14365
   776
  show ?thesis 
paulson@14365
   777
  proof (rule classical)
paulson@14365
   778
    assume "~(\<exists>r\<in>A. r * x \<notin> A)"
paulson@14365
   779
    with y have ymem: "y * x \<in> A" by blast 
paulson@14365
   780
    from ypos mult_strict_left_mono [OF x]
paulson@14365
   781
    have yless: "y < y*x" by simp 
paulson@14365
   782
    let ?d = "y*x - y"
paulson@14365
   783
    from yless have dpos: "0 < ?d" and eq: "y + ?d = y*x" by auto
paulson@14365
   784
    from Gleason9_34 [OF A dpos]
paulson@14365
   785
    obtain r where r: "r\<in>A" and notin: "r + ?d \<notin> A" ..
paulson@14365
   786
    have rpos: "0<r" by (rule preal_imp_pos [OF A r])
paulson@14365
   787
    with dpos have rdpos: "0 < r + ?d" by arith
paulson@14365
   788
    have "~ (r + ?d \<le> y + ?d)"
paulson@14365
   789
    proof
paulson@14365
   790
      assume le: "r + ?d \<le> y + ?d" 
paulson@14365
   791
      from ymem have yd: "y + ?d \<in> A" by (simp add: eq)
paulson@14365
   792
      have "r + ?d \<in> A" by (rule preal_downwards_closed' [OF A yd rdpos le])
paulson@14365
   793
      with notin show False by simp
paulson@14365
   794
    qed
paulson@14365
   795
    hence "y < r" by simp
paulson@14365
   796
    with ypos have  dless: "?d < (r * ?d)/y"
paulson@14365
   797
      by (simp add: pos_less_divide_eq mult_commute [of ?d]
paulson@14365
   798
                    mult_strict_right_mono dpos)
paulson@14365
   799
    have "r + ?d < r*x"
paulson@14365
   800
    proof -
paulson@14365
   801
      have "r + ?d < r + (r * ?d)/y" by (simp add: dless)
paulson@14365
   802
      also with ypos have "... = (r/y) * (y + ?d)"
paulson@14430
   803
	by (simp only: right_distrib divide_inverse mult_ac, simp)
paulson@14365
   804
      also have "... = r*x" using ypos
paulson@15234
   805
	by (simp add: times_divide_eq_left) 
paulson@14365
   806
      finally show "r + ?d < r*x" .
paulson@14365
   807
    qed
paulson@14365
   808
    with r notin rdpos
paulson@14365
   809
    show "\<exists>r\<in>A. r * x \<notin> A" by (blast dest:  preal_downwards_closed [OF A])
paulson@14365
   810
  qed  
paulson@14365
   811
qed
paulson@14335
   812
paulson@14365
   813
subsection{*Existence of Inverse: Part 2*}
paulson@14365
   814
paulson@14365
   815
lemma mem_Rep_preal_inverse_iff:
paulson@14365
   816
      "(z \<in> Rep_preal(inverse R)) = 
paulson@14365
   817
       (0 < z \<and> (\<exists>y. z < y \<and> inverse y \<notin> Rep_preal R))"
paulson@14365
   818
apply (simp add: preal_inverse_def mem_inverse_set Rep_preal)
paulson@14365
   819
apply (simp add: inverse_set_def) 
paulson@14335
   820
done
paulson@14335
   821
paulson@14365
   822
lemma Rep_preal_of_rat:
paulson@14365
   823
     "0 < q ==> Rep_preal (preal_of_rat q) = {x. 0 < x \<and> x < q}"
paulson@14365
   824
by (simp add: preal_of_rat_def rat_mem_preal) 
paulson@14365
   825
paulson@14365
   826
lemma subset_inverse_mult_lemma:
paulson@14365
   827
      assumes xpos: "0 < x" and xless: "x < 1"
paulson@14365
   828
         shows "\<exists>r u y. 0 < r & r < y & inverse y \<notin> Rep_preal R & 
paulson@14365
   829
                        u \<in> Rep_preal R & x = r * u"
paulson@14365
   830
proof -
paulson@14365
   831
  from xpos and xless have "1 < inverse x" by (simp add: one_less_inverse_iff)
paulson@14365
   832
  from lemma_gleason9_36 [OF Rep_preal this]
paulson@14365
   833
  obtain r where r: "r \<in> Rep_preal R" 
paulson@14365
   834
             and notin: "r * (inverse x) \<notin> Rep_preal R" ..
paulson@14365
   835
  have rpos: "0<r" by (rule preal_imp_pos [OF Rep_preal r])
paulson@14365
   836
  from preal_exists_greater [OF Rep_preal r]
paulson@14365
   837
  obtain u where u: "u \<in> Rep_preal R" and rless: "r < u" ..
paulson@14365
   838
  have upos: "0<u" by (rule preal_imp_pos [OF Rep_preal u])
paulson@14365
   839
  show ?thesis
paulson@14365
   840
  proof (intro exI conjI)
paulson@14365
   841
    show "0 < x/u" using xpos upos
paulson@14365
   842
      by (simp add: zero_less_divide_iff)  
paulson@14365
   843
    show "x/u < x/r" using xpos upos rpos
paulson@14430
   844
      by (simp add: divide_inverse mult_less_cancel_left rless) 
paulson@14365
   845
    show "inverse (x / r) \<notin> Rep_preal R" using notin
paulson@14430
   846
      by (simp add: divide_inverse mult_commute) 
paulson@14365
   847
    show "u \<in> Rep_preal R" by (rule u) 
paulson@14365
   848
    show "x = x / u * u" using upos 
paulson@14430
   849
      by (simp add: divide_inverse mult_commute) 
paulson@14365
   850
  qed
paulson@14365
   851
qed
paulson@14365
   852
paulson@14365
   853
lemma subset_inverse_mult: 
paulson@14365
   854
     "Rep_preal(preal_of_rat 1) \<subseteq> Rep_preal(inverse R * R)"
paulson@14365
   855
apply (auto simp add: Bex_def Rep_preal_of_rat mem_Rep_preal_inverse_iff 
paulson@14365
   856
                      mem_Rep_preal_mult_iff)
paulson@14365
   857
apply (blast dest: subset_inverse_mult_lemma) 
paulson@14335
   858
done
paulson@14335
   859
paulson@14365
   860
lemma inverse_mult_subset_lemma:
paulson@14365
   861
     assumes rpos: "0 < r" 
paulson@14365
   862
         and rless: "r < y"
paulson@14365
   863
         and notin: "inverse y \<notin> Rep_preal R"
paulson@14365
   864
         and q: "q \<in> Rep_preal R"
paulson@14365
   865
     shows "r*q < 1"
paulson@14365
   866
proof -
paulson@14365
   867
  have "q < inverse y" using rpos rless
paulson@14365
   868
    by (simp add: not_in_preal_ub [OF Rep_preal notin] q)
paulson@14365
   869
  hence "r * q < r/y" using rpos
paulson@14430
   870
    by (simp add: divide_inverse mult_less_cancel_left)
paulson@14365
   871
  also have "... \<le> 1" using rpos rless
paulson@14365
   872
    by (simp add: pos_divide_le_eq)
paulson@14365
   873
  finally show ?thesis .
paulson@14365
   874
qed
paulson@14365
   875
paulson@14365
   876
lemma inverse_mult_subset:
paulson@14365
   877
     "Rep_preal(inverse R * R) \<subseteq> Rep_preal(preal_of_rat 1)"
paulson@14365
   878
apply (auto simp add: Bex_def Rep_preal_of_rat mem_Rep_preal_inverse_iff 
paulson@14365
   879
                      mem_Rep_preal_mult_iff)
paulson@14365
   880
apply (simp add: zero_less_mult_iff preal_imp_pos [OF Rep_preal]) 
paulson@14365
   881
apply (blast intro: inverse_mult_subset_lemma) 
paulson@14365
   882
done
paulson@14365
   883
paulson@15413
   884
lemma preal_mult_inverse: "inverse R * R = (preal_of_rat 1)"
paulson@15413
   885
apply (rule Rep_preal_inject [THEN iffD1])
paulson@14365
   886
apply (rule equalityI [OF inverse_mult_subset subset_inverse_mult]) 
paulson@14365
   887
done
paulson@14365
   888
paulson@15413
   889
lemma preal_mult_inverse_right: "R * inverse R = (preal_of_rat 1)"
paulson@14365
   890
apply (rule preal_mult_commute [THEN subst])
paulson@14365
   891
apply (rule preal_mult_inverse)
paulson@14335
   892
done
paulson@14335
   893
paulson@14335
   894
paulson@14365
   895
text{*Theorems needing @{text Gleason9_34}*}
paulson@14335
   896
paulson@14365
   897
lemma Rep_preal_self_subset: "Rep_preal (R) \<subseteq> Rep_preal(R + S)"
paulson@14365
   898
proof 
paulson@14365
   899
  fix r
paulson@14365
   900
  assume r: "r \<in> Rep_preal R"
paulson@14365
   901
  have rpos: "0<r" by (rule preal_imp_pos [OF Rep_preal r])
paulson@14365
   902
  from mem_Rep_preal_Ex 
paulson@14365
   903
  obtain y where y: "y \<in> Rep_preal S" ..
paulson@14365
   904
  have ypos: "0<y" by (rule preal_imp_pos [OF Rep_preal y])
paulson@14365
   905
  have ry: "r+y \<in> Rep_preal(R + S)" using r y
paulson@14365
   906
    by (auto simp add: mem_Rep_preal_add_iff)
paulson@14365
   907
  show "r \<in> Rep_preal(R + S)" using r ypos rpos 
paulson@14365
   908
    by (simp add:  preal_downwards_closed [OF Rep_preal ry]) 
paulson@14365
   909
qed
paulson@14335
   910
paulson@14365
   911
lemma Rep_preal_sum_not_subset: "~ Rep_preal (R + S) \<subseteq> Rep_preal(R)"
paulson@14365
   912
proof -
paulson@14365
   913
  from mem_Rep_preal_Ex 
paulson@14365
   914
  obtain y where y: "y \<in> Rep_preal S" ..
paulson@14365
   915
  have ypos: "0<y" by (rule preal_imp_pos [OF Rep_preal y])
paulson@14365
   916
  from  Gleason9_34 [OF Rep_preal ypos]
paulson@14365
   917
  obtain r where r: "r \<in> Rep_preal R" and notin: "r + y \<notin> Rep_preal R" ..
paulson@14365
   918
  have "r + y \<in> Rep_preal (R + S)" using r y
paulson@14365
   919
    by (auto simp add: mem_Rep_preal_add_iff)
paulson@14365
   920
  thus ?thesis using notin by blast
paulson@14365
   921
qed
paulson@14335
   922
paulson@14365
   923
lemma Rep_preal_sum_not_eq: "Rep_preal (R + S) \<noteq> Rep_preal(R)"
paulson@14365
   924
by (insert Rep_preal_sum_not_subset, blast)
paulson@14335
   925
paulson@14335
   926
text{*at last, Gleason prop. 9-3.5(iii) page 123*}
paulson@14365
   927
lemma preal_self_less_add_left: "(R::preal) < R + S"
paulson@14335
   928
apply (unfold preal_less_def psubset_def)
paulson@14335
   929
apply (simp add: Rep_preal_self_subset Rep_preal_sum_not_eq [THEN not_sym])
paulson@14335
   930
done
paulson@14335
   931
paulson@14365
   932
lemma preal_self_less_add_right: "(R::preal) < S + R"
paulson@14365
   933
by (simp add: preal_add_commute preal_self_less_add_left)
paulson@14365
   934
paulson@14365
   935
lemma preal_not_eq_self: "x \<noteq> x + (y::preal)"
paulson@14365
   936
by (insert preal_self_less_add_left [of x y], auto)
paulson@14335
   937
paulson@14335
   938
paulson@14365
   939
subsection{*Subtraction for Positive Reals*}
paulson@14335
   940
paulson@14365
   941
text{*Gleason prop. 9-3.5(iv), page 123: proving @{term "A < B ==> \<exists>D. A + D =
paulson@14365
   942
B"}. We define the claimed @{term D} and show that it is a positive real*}
paulson@14335
   943
paulson@14335
   944
text{*Part 1 of Dedekind sections definition*}
paulson@14365
   945
lemma diff_set_not_empty:
paulson@14365
   946
     "R < S ==> {} \<subset> diff_set (Rep_preal S) (Rep_preal R)"
paulson@14365
   947
apply (auto simp add: preal_less_def diff_set_def elim!: equalityE) 
paulson@14365
   948
apply (frule_tac x1 = S in Rep_preal [THEN preal_exists_greater])
paulson@14365
   949
apply (drule preal_imp_pos [OF Rep_preal], clarify)
paulson@14365
   950
apply (cut_tac a=x and b=u in add_eq_exists, force) 
paulson@14335
   951
done
paulson@14335
   952
paulson@14335
   953
text{*Part 2 of Dedekind sections definition*}
paulson@14365
   954
lemma diff_set_nonempty:
paulson@14365
   955
     "\<exists>q. 0 < q & q \<notin> diff_set (Rep_preal S) (Rep_preal R)"
paulson@14365
   956
apply (cut_tac X = S in Rep_preal_exists_bound)
paulson@14335
   957
apply (erule exE)
paulson@14335
   958
apply (rule_tac x = x in exI, auto)
paulson@14365
   959
apply (simp add: diff_set_def) 
paulson@14365
   960
apply (auto dest: Rep_preal [THEN preal_downwards_closed])
paulson@14335
   961
done
paulson@14335
   962
paulson@14365
   963
lemma diff_set_not_rat_set:
paulson@14365
   964
     "diff_set (Rep_preal S) (Rep_preal R) < {r. 0 < r}" (is "?lhs < ?rhs")
paulson@14365
   965
proof
paulson@14365
   966
  show "?lhs \<subseteq> ?rhs" by (auto simp add: diff_set_def) 
paulson@14365
   967
  show "?lhs \<noteq> ?rhs" using diff_set_nonempty by blast
paulson@14365
   968
qed
paulson@14335
   969
paulson@14335
   970
text{*Part 3 of Dedekind sections definition*}
paulson@14365
   971
lemma diff_set_lemma3:
paulson@14365
   972
     "[|R < S; u \<in> diff_set (Rep_preal S) (Rep_preal R); 0 < z; z < u|] 
paulson@14365
   973
      ==> z \<in> diff_set (Rep_preal S) (Rep_preal R)"
paulson@14365
   974
apply (auto simp add: diff_set_def) 
paulson@14365
   975
apply (rule_tac x=x in exI) 
paulson@14365
   976
apply (drule Rep_preal [THEN preal_downwards_closed], auto)
paulson@14335
   977
done
paulson@14335
   978
paulson@14365
   979
text{*Part 4 of Dedekind sections definition*}
paulson@14365
   980
lemma diff_set_lemma4:
paulson@14365
   981
     "[|R < S; y \<in> diff_set (Rep_preal S) (Rep_preal R)|] 
paulson@14365
   982
      ==> \<exists>u \<in> diff_set (Rep_preal S) (Rep_preal R). y < u"
paulson@14365
   983
apply (auto simp add: diff_set_def) 
paulson@14365
   984
apply (drule Rep_preal [THEN preal_exists_greater], clarify) 
paulson@14365
   985
apply (cut_tac a="x+y" and b=u in add_eq_exists, clarify)  
paulson@14365
   986
apply (rule_tac x="y+xa" in exI) 
paulson@14365
   987
apply (auto simp add: add_ac)
paulson@14335
   988
done
paulson@14335
   989
paulson@14365
   990
lemma mem_diff_set:
paulson@14365
   991
     "R < S ==> diff_set (Rep_preal S) (Rep_preal R) \<in> preal"
paulson@14365
   992
apply (unfold preal_def cut_def)
paulson@14365
   993
apply (blast intro!: diff_set_not_empty diff_set_not_rat_set
paulson@14365
   994
                     diff_set_lemma3 diff_set_lemma4)
paulson@14365
   995
done
paulson@14365
   996
paulson@14365
   997
lemma mem_Rep_preal_diff_iff:
paulson@14365
   998
      "R < S ==>
paulson@14365
   999
       (z \<in> Rep_preal(S-R)) = 
paulson@14365
  1000
       (\<exists>x. 0 < x & 0 < z & x \<notin> Rep_preal R & x + z \<in> Rep_preal S)"
paulson@14365
  1001
apply (simp add: preal_diff_def mem_diff_set Rep_preal)
paulson@14365
  1002
apply (force simp add: diff_set_def) 
paulson@14335
  1003
done
paulson@14335
  1004
paulson@14365
  1005
paulson@14365
  1006
text{*proving that @{term "R + D \<le> S"}*}
paulson@14365
  1007
paulson@14365
  1008
lemma less_add_left_lemma:
paulson@14365
  1009
  assumes Rless: "R < S"
paulson@14365
  1010
      and a: "a \<in> Rep_preal R"
paulson@14365
  1011
      and cb: "c + b \<in> Rep_preal S"
paulson@14365
  1012
      and "c \<notin> Rep_preal R"
paulson@14365
  1013
      and "0 < b"
paulson@14365
  1014
      and "0 < c"
paulson@14365
  1015
  shows "a + b \<in> Rep_preal S"
paulson@14365
  1016
proof -
paulson@14365
  1017
  have "0<a" by (rule preal_imp_pos [OF Rep_preal a])
paulson@14365
  1018
  moreover
paulson@14365
  1019
  have "a < c" using prems
paulson@14365
  1020
    by (blast intro: not_in_Rep_preal_ub ) 
paulson@14365
  1021
  ultimately show ?thesis using prems
paulson@14365
  1022
    by (simp add: preal_downwards_closed [OF Rep_preal cb]) 
paulson@14365
  1023
qed
paulson@14365
  1024
paulson@14365
  1025
lemma less_add_left_le1:
paulson@14365
  1026
       "R < (S::preal) ==> R + (S-R) \<le> S"
paulson@14365
  1027
apply (auto simp add: Bex_def preal_le_def mem_Rep_preal_add_iff 
paulson@14365
  1028
                      mem_Rep_preal_diff_iff)
paulson@14365
  1029
apply (blast intro: less_add_left_lemma) 
paulson@14335
  1030
done
paulson@14335
  1031
paulson@14365
  1032
subsection{*proving that @{term "S \<le> R + D"} --- trickier*}
paulson@14335
  1033
paulson@14335
  1034
lemma lemma_sum_mem_Rep_preal_ex:
paulson@14365
  1035
     "x \<in> Rep_preal S ==> \<exists>e. 0 < e & x + e \<in> Rep_preal S"
paulson@14365
  1036
apply (drule Rep_preal [THEN preal_exists_greater], clarify) 
paulson@14365
  1037
apply (cut_tac a=x and b=u in add_eq_exists, auto) 
paulson@14335
  1038
done
paulson@14335
  1039
paulson@14365
  1040
lemma less_add_left_lemma2:
paulson@14365
  1041
  assumes Rless: "R < S"
paulson@14365
  1042
      and x:     "x \<in> Rep_preal S"
paulson@14365
  1043
      and xnot: "x \<notin>  Rep_preal R"
paulson@14365
  1044
  shows "\<exists>u v z. 0 < v & 0 < z & u \<in> Rep_preal R & z \<notin> Rep_preal R & 
paulson@14365
  1045
                     z + v \<in> Rep_preal S & x = u + v"
paulson@14365
  1046
proof -
paulson@14365
  1047
  have xpos: "0<x" by (rule preal_imp_pos [OF Rep_preal x])
paulson@14365
  1048
  from lemma_sum_mem_Rep_preal_ex [OF x]
paulson@14365
  1049
  obtain e where epos: "0 < e" and xe: "x + e \<in> Rep_preal S" by blast
paulson@14365
  1050
  from  Gleason9_34 [OF Rep_preal epos]
paulson@14365
  1051
  obtain r where r: "r \<in> Rep_preal R" and notin: "r + e \<notin> Rep_preal R" ..
paulson@14365
  1052
  with x xnot xpos have rless: "r < x" by (blast intro: not_in_Rep_preal_ub)
paulson@14365
  1053
  from add_eq_exists [of r x]
paulson@14365
  1054
  obtain y where eq: "x = r+y" by auto
paulson@14365
  1055
  show ?thesis 
paulson@14365
  1056
  proof (intro exI conjI)
paulson@14365
  1057
    show "r \<in> Rep_preal R" by (rule r)
paulson@14365
  1058
    show "r + e \<notin> Rep_preal R" by (rule notin)
paulson@14365
  1059
    show "r + e + y \<in> Rep_preal S" using xe eq by (simp add: add_ac)
paulson@14365
  1060
    show "x = r + y" by (simp add: eq)
paulson@14365
  1061
    show "0 < r + e" using epos preal_imp_pos [OF Rep_preal r]
paulson@14365
  1062
      by simp
paulson@14365
  1063
    show "0 < y" using rless eq by arith
paulson@14365
  1064
  qed
paulson@14365
  1065
qed
paulson@14365
  1066
paulson@14365
  1067
lemma less_add_left_le2: "R < (S::preal) ==> S \<le> R + (S-R)"
paulson@14365
  1068
apply (auto simp add: preal_le_def)
paulson@14365
  1069
apply (case_tac "x \<in> Rep_preal R")
paulson@14365
  1070
apply (cut_tac Rep_preal_self_subset [of R], force)
paulson@14365
  1071
apply (auto simp add: Bex_def mem_Rep_preal_add_iff mem_Rep_preal_diff_iff)
paulson@14365
  1072
apply (blast dest: less_add_left_lemma2)
paulson@14335
  1073
done
paulson@14335
  1074
paulson@14365
  1075
lemma less_add_left: "R < (S::preal) ==> R + (S-R) = S"
paulson@14365
  1076
by (blast intro: preal_le_anti_sym [OF less_add_left_le1 less_add_left_le2])
paulson@14335
  1077
paulson@14365
  1078
lemma less_add_left_Ex: "R < (S::preal) ==> \<exists>D. R + D = S"
paulson@14365
  1079
by (fast dest: less_add_left)
paulson@14335
  1080
paulson@14365
  1081
lemma preal_add_less2_mono1: "R < (S::preal) ==> R + T < S + T"
paulson@14365
  1082
apply (auto dest!: less_add_left_Ex simp add: preal_add_assoc)
paulson@14335
  1083
apply (rule_tac y1 = D in preal_add_commute [THEN subst])
paulson@14335
  1084
apply (auto intro: preal_self_less_add_left simp add: preal_add_assoc [symmetric])
paulson@14335
  1085
done
paulson@14335
  1086
paulson@14365
  1087
lemma preal_add_less2_mono2: "R < (S::preal) ==> T + R < T + S"
paulson@14365
  1088
by (auto intro: preal_add_less2_mono1 simp add: preal_add_commute [of T])
paulson@14335
  1089
paulson@14365
  1090
lemma preal_add_right_less_cancel: "R + T < S + T ==> R < (S::preal)"
paulson@14365
  1091
apply (insert linorder_less_linear [of R S], auto)
paulson@14365
  1092
apply (drule_tac R = S and T = T in preal_add_less2_mono1)
paulson@14365
  1093
apply (blast dest: order_less_trans) 
paulson@14335
  1094
done
paulson@14335
  1095
paulson@14365
  1096
lemma preal_add_left_less_cancel: "T + R < T + S ==> R <  (S::preal)"
paulson@14365
  1097
by (auto elim: preal_add_right_less_cancel simp add: preal_add_commute [of T])
paulson@14335
  1098
paulson@14365
  1099
lemma preal_add_less_cancel_right: "((R::preal) + T < S + T) = (R < S)"
paulson@14335
  1100
by (blast intro: preal_add_less2_mono1 preal_add_right_less_cancel)
paulson@14335
  1101
paulson@14365
  1102
lemma preal_add_less_cancel_left: "(T + (R::preal) < T + S) = (R < S)"
paulson@14335
  1103
by (blast intro: preal_add_less2_mono2 preal_add_left_less_cancel)
paulson@14335
  1104
paulson@14365
  1105
lemma preal_add_le_cancel_right: "((R::preal) + T \<le> S + T) = (R \<le> S)"
paulson@14365
  1106
by (simp add: linorder_not_less [symmetric] preal_add_less_cancel_right) 
paulson@14365
  1107
paulson@14365
  1108
lemma preal_add_le_cancel_left: "(T + (R::preal) \<le> T + S) = (R \<le> S)"
paulson@14365
  1109
by (simp add: linorder_not_less [symmetric] preal_add_less_cancel_left) 
paulson@14365
  1110
paulson@14335
  1111
lemma preal_add_less_mono:
paulson@14335
  1112
     "[| x1 < y1; x2 < y2 |] ==> x1 + x2 < y1 + (y2::preal)"
paulson@14365
  1113
apply (auto dest!: less_add_left_Ex simp add: preal_add_ac)
paulson@14335
  1114
apply (rule preal_add_assoc [THEN subst])
paulson@14335
  1115
apply (rule preal_self_less_add_right)
paulson@14335
  1116
done
paulson@14335
  1117
paulson@14365
  1118
lemma preal_add_right_cancel: "(R::preal) + T = S + T ==> R = S"
paulson@14365
  1119
apply (insert linorder_less_linear [of R S], safe)
paulson@14365
  1120
apply (drule_tac [!] T = T in preal_add_less2_mono1, auto)
paulson@14335
  1121
done
paulson@14335
  1122
paulson@14365
  1123
lemma preal_add_left_cancel: "C + A = C + B ==> A = (B::preal)"
paulson@14335
  1124
by (auto intro: preal_add_right_cancel simp add: preal_add_commute)
paulson@14335
  1125
paulson@14365
  1126
lemma preal_add_left_cancel_iff: "(C + A = C + B) = ((A::preal) = B)"
paulson@14335
  1127
by (fast intro: preal_add_left_cancel)
paulson@14335
  1128
paulson@14365
  1129
lemma preal_add_right_cancel_iff: "(A + C = B + C) = ((A::preal) = B)"
paulson@14335
  1130
by (fast intro: preal_add_right_cancel)
paulson@14335
  1131
paulson@14365
  1132
lemmas preal_cancels =
paulson@14365
  1133
    preal_add_less_cancel_right preal_add_less_cancel_left
paulson@14365
  1134
    preal_add_le_cancel_right preal_add_le_cancel_left
paulson@14365
  1135
    preal_add_left_cancel_iff preal_add_right_cancel_iff
paulson@14335
  1136
paulson@14335
  1137
paulson@14335
  1138
subsection{*Completeness of type @{typ preal}*}
paulson@14335
  1139
paulson@14335
  1140
text{*Prove that supremum is a cut*}
paulson@14335
  1141
paulson@14365
  1142
text{*Part 1 of Dedekind sections definition*}
paulson@14365
  1143
paulson@14365
  1144
lemma preal_sup_set_not_empty:
paulson@14365
  1145
     "P \<noteq> {} ==> {} \<subset> (\<Union>X \<in> P. Rep_preal(X))"
paulson@14365
  1146
apply auto
paulson@14365
  1147
apply (cut_tac X = x in mem_Rep_preal_Ex, auto)
paulson@14335
  1148
done
paulson@14335
  1149
paulson@14335
  1150
paulson@14335
  1151
text{*Part 2 of Dedekind sections definition*}
paulson@14365
  1152
paulson@14365
  1153
lemma preal_sup_not_exists:
paulson@14365
  1154
     "\<forall>X \<in> P. X \<le> Y ==> \<exists>q. 0 < q & q \<notin> (\<Union>X \<in> P. Rep_preal(X))"
paulson@14365
  1155
apply (cut_tac X = Y in Rep_preal_exists_bound)
paulson@14365
  1156
apply (auto simp add: preal_le_def)
paulson@14335
  1157
done
paulson@14335
  1158
paulson@14365
  1159
lemma preal_sup_set_not_rat_set:
paulson@14365
  1160
     "\<forall>X \<in> P. X \<le> Y ==> (\<Union>X \<in> P. Rep_preal(X)) < {r. 0 < r}"
paulson@14365
  1161
apply (drule preal_sup_not_exists)
paulson@14365
  1162
apply (blast intro: preal_imp_pos [OF Rep_preal])  
paulson@14335
  1163
done
paulson@14335
  1164
paulson@14335
  1165
text{*Part 3 of Dedekind sections definition*}
paulson@14335
  1166
lemma preal_sup_set_lemma3:
paulson@14365
  1167
     "[|P \<noteq> {}; \<forall>X \<in> P. X \<le> Y; u \<in> (\<Union>X \<in> P. Rep_preal(X)); 0 < z; z < u|]
paulson@14365
  1168
      ==> z \<in> (\<Union>X \<in> P. Rep_preal(X))"
paulson@14365
  1169
by (auto elim: Rep_preal [THEN preal_downwards_closed])
paulson@14335
  1170
paulson@14365
  1171
text{*Part 4 of Dedekind sections definition*}
paulson@14335
  1172
lemma preal_sup_set_lemma4:
paulson@14365
  1173
     "[|P \<noteq> {}; \<forall>X \<in> P. X \<le> Y; y \<in> (\<Union>X \<in> P. Rep_preal(X)) |]
paulson@14365
  1174
          ==> \<exists>u \<in> (\<Union>X \<in> P. Rep_preal(X)). y < u"
paulson@14365
  1175
by (blast dest: Rep_preal [THEN preal_exists_greater])
paulson@14335
  1176
paulson@14335
  1177
lemma preal_sup:
paulson@14365
  1178
     "[|P \<noteq> {}; \<forall>X \<in> P. X \<le> Y|] ==> (\<Union>X \<in> P. Rep_preal(X)) \<in> preal"
paulson@14365
  1179
apply (unfold preal_def cut_def)
paulson@14365
  1180
apply (blast intro!: preal_sup_set_not_empty preal_sup_set_not_rat_set
paulson@14365
  1181
                     preal_sup_set_lemma3 preal_sup_set_lemma4)
paulson@14335
  1182
done
paulson@14335
  1183
paulson@14365
  1184
lemma preal_psup_le:
paulson@14365
  1185
     "[| \<forall>X \<in> P. X \<le> Y;  x \<in> P |] ==> x \<le> psup P"
paulson@14365
  1186
apply (simp (no_asm_simp) add: preal_le_def) 
paulson@14365
  1187
apply (subgoal_tac "P \<noteq> {}") 
paulson@14365
  1188
apply (auto simp add: psup_def preal_sup) 
paulson@14335
  1189
done
paulson@14335
  1190
paulson@14365
  1191
lemma psup_le_ub: "[| P \<noteq> {}; \<forall>X \<in> P. X \<le> Y |] ==> psup P \<le> Y"
paulson@14365
  1192
apply (simp (no_asm_simp) add: preal_le_def)
paulson@14365
  1193
apply (simp add: psup_def preal_sup) 
paulson@14335
  1194
apply (auto simp add: preal_le_def)
paulson@14335
  1195
done
paulson@14335
  1196
paulson@14335
  1197
text{*Supremum property*}
paulson@14335
  1198
lemma preal_complete:
paulson@14365
  1199
     "[| P \<noteq> {}; \<forall>X \<in> P. X \<le> Y |] ==> (\<exists>X \<in> P. Z < X) = (Z < psup P)"
paulson@14365
  1200
apply (simp add: preal_less_def psup_def preal_sup)
paulson@14365
  1201
apply (auto simp add: preal_le_def)
paulson@14365
  1202
apply (rename_tac U) 
paulson@14365
  1203
apply (cut_tac x = U and y = Z in linorder_less_linear)
paulson@14365
  1204
apply (auto simp add: preal_less_def)
paulson@14335
  1205
done
paulson@14335
  1206
paulson@14335
  1207
paulson@14365
  1208
subsection{*The Embadding from @{typ rat} into @{typ preal}*}
paulson@14335
  1209
paulson@14365
  1210
lemma preal_of_rat_add_lemma1:
paulson@14365
  1211
     "[|x < y + z; 0 < x; 0 < y|] ==> x * y * inverse (y + z) < (y::rat)"
paulson@14365
  1212
apply (frule_tac c = "y * inverse (y + z) " in mult_strict_right_mono)
paulson@14365
  1213
apply (simp add: zero_less_mult_iff) 
paulson@14365
  1214
apply (simp add: mult_ac)
paulson@14335
  1215
done
paulson@14335
  1216
paulson@14365
  1217
lemma preal_of_rat_add_lemma2:
paulson@14365
  1218
  assumes "u < x + y"
paulson@14365
  1219
      and "0 < x"
paulson@14365
  1220
      and "0 < y"
paulson@14365
  1221
      and "0 < u"
paulson@14365
  1222
  shows "\<exists>v w::rat. w < y & 0 < v & v < x & 0 < w & u = v + w"
paulson@14365
  1223
proof (intro exI conjI)
paulson@14365
  1224
  show "u * x * inverse(x+y) < x" using prems 
paulson@14365
  1225
    by (simp add: preal_of_rat_add_lemma1) 
paulson@14365
  1226
  show "u * y * inverse(x+y) < y" using prems 
paulson@14365
  1227
    by (simp add: preal_of_rat_add_lemma1 add_commute [of x]) 
paulson@14365
  1228
  show "0 < u * x * inverse (x + y)" using prems
paulson@14365
  1229
    by (simp add: zero_less_mult_iff) 
paulson@14365
  1230
  show "0 < u * y * inverse (x + y)" using prems
paulson@14365
  1231
    by (simp add: zero_less_mult_iff) 
paulson@14365
  1232
  show "u = u * x * inverse (x + y) + u * y * inverse (x + y)" using prems
paulson@14365
  1233
    by (simp add: left_distrib [symmetric] right_distrib [symmetric] mult_ac)
paulson@14365
  1234
qed
paulson@14365
  1235
paulson@14365
  1236
lemma preal_of_rat_add:
paulson@14365
  1237
     "[| 0 < x; 0 < y|] 
paulson@14365
  1238
      ==> preal_of_rat ((x::rat) + y) = preal_of_rat x + preal_of_rat y"
paulson@14365
  1239
apply (unfold preal_of_rat_def preal_add_def)
paulson@14365
  1240
apply (simp add: rat_mem_preal) 
paulson@14335
  1241
apply (rule_tac f = Abs_preal in arg_cong)
paulson@14365
  1242
apply (auto simp add: add_set_def) 
paulson@14365
  1243
apply (blast dest: preal_of_rat_add_lemma2) 
paulson@14365
  1244
done
paulson@14365
  1245
paulson@14365
  1246
lemma preal_of_rat_mult_lemma1:
paulson@14365
  1247
     "[|x < y; 0 < x; 0 < z|] ==> x * z * inverse y < (z::rat)"
paulson@14365
  1248
apply (frule_tac c = "z * inverse y" in mult_strict_right_mono)
paulson@14365
  1249
apply (simp add: zero_less_mult_iff)
paulson@14365
  1250
apply (subgoal_tac "y * (z * inverse y) = z * (y * inverse y)")
paulson@14365
  1251
apply (simp_all add: mult_ac)
paulson@14335
  1252
done
paulson@14335
  1253
paulson@14365
  1254
lemma preal_of_rat_mult_lemma2: 
paulson@14365
  1255
  assumes xless: "x < y * z"
paulson@14365
  1256
      and xpos: "0 < x"
paulson@14365
  1257
      and ypos: "0 < y"
paulson@14365
  1258
  shows "x * z * inverse y * inverse z < (z::rat)"
paulson@14365
  1259
proof -
paulson@14365
  1260
  have "0 < y * z" using prems by simp
paulson@14365
  1261
  hence zpos:  "0 < z" using prems by (simp add: zero_less_mult_iff)
paulson@14365
  1262
  have "x * z * inverse y * inverse z = x * inverse y * (z * inverse z)"
paulson@14365
  1263
    by (simp add: mult_ac)
paulson@14365
  1264
  also have "... = x/y" using zpos
paulson@14430
  1265
    by (simp add: divide_inverse)
paulson@14365
  1266
  also have "... < z"
paulson@14365
  1267
    by (simp add: pos_divide_less_eq [OF ypos] mult_commute) 
paulson@14365
  1268
  finally show ?thesis .
paulson@14365
  1269
qed
paulson@14335
  1270
paulson@14365
  1271
lemma preal_of_rat_mult_lemma3:
paulson@14365
  1272
  assumes uless: "u < x * y"
paulson@14365
  1273
      and "0 < x"
paulson@14365
  1274
      and "0 < y"
paulson@14365
  1275
      and "0 < u"
paulson@14365
  1276
  shows "\<exists>v w::rat. v < x & w < y & 0 < v & 0 < w & u = v * w"
paulson@14365
  1277
proof -
paulson@14365
  1278
  from dense [OF uless] 
paulson@14365
  1279
  obtain r where "u < r" "r < x * y" by blast
paulson@14365
  1280
  thus ?thesis
paulson@14365
  1281
  proof (intro exI conjI)
paulson@14365
  1282
  show "u * x * inverse r < x" using prems 
paulson@14365
  1283
    by (simp add: preal_of_rat_mult_lemma1) 
paulson@14365
  1284
  show "r * y * inverse x * inverse y < y" using prems
paulson@14365
  1285
    by (simp add: preal_of_rat_mult_lemma2)
paulson@14365
  1286
  show "0 < u * x * inverse r" using prems
paulson@14365
  1287
    by (simp add: zero_less_mult_iff) 
paulson@14365
  1288
  show "0 < r * y * inverse x * inverse y" using prems
paulson@14365
  1289
    by (simp add: zero_less_mult_iff) 
paulson@14365
  1290
  have "u * x * inverse r * (r * y * inverse x * inverse y) =
paulson@14365
  1291
        u * (r * inverse r) * (x * inverse x) * (y * inverse y)"
paulson@14365
  1292
    by (simp only: mult_ac)
paulson@14365
  1293
  thus "u = u * x * inverse r * (r * y * inverse x * inverse y)" using prems
paulson@14365
  1294
    by simp
paulson@14365
  1295
  qed
paulson@14365
  1296
qed
paulson@14365
  1297
paulson@14365
  1298
lemma preal_of_rat_mult:
paulson@14365
  1299
     "[| 0 < x; 0 < y|] 
paulson@14365
  1300
      ==> preal_of_rat ((x::rat) * y) = preal_of_rat x * preal_of_rat y"
paulson@14365
  1301
apply (unfold preal_of_rat_def preal_mult_def)
paulson@14365
  1302
apply (simp add: rat_mem_preal) 
paulson@14365
  1303
apply (rule_tac f = Abs_preal in arg_cong)
paulson@14365
  1304
apply (auto simp add: zero_less_mult_iff mult_strict_mono mult_set_def) 
paulson@14365
  1305
apply (blast dest: preal_of_rat_mult_lemma3) 
paulson@14335
  1306
done
paulson@14335
  1307
paulson@14365
  1308
lemma preal_of_rat_less_iff:
paulson@14365
  1309
      "[| 0 < x; 0 < y|] ==> (preal_of_rat x < preal_of_rat y) = (x < y)"
paulson@14365
  1310
by (force simp add: preal_of_rat_def preal_less_def rat_mem_preal) 
paulson@14335
  1311
paulson@14365
  1312
lemma preal_of_rat_le_iff:
paulson@14365
  1313
      "[| 0 < x; 0 < y|] ==> (preal_of_rat x \<le> preal_of_rat y) = (x \<le> y)"
paulson@14365
  1314
by (simp add: preal_of_rat_less_iff linorder_not_less [symmetric]) 
paulson@14365
  1315
paulson@14365
  1316
lemma preal_of_rat_eq_iff:
paulson@14365
  1317
      "[| 0 < x; 0 < y|] ==> (preal_of_rat x = preal_of_rat y) = (x = y)"
paulson@14365
  1318
by (simp add: preal_of_rat_le_iff order_eq_iff) 
paulson@14335
  1319
paulson@14335
  1320
paulson@14335
  1321
ML
paulson@14335
  1322
{*
paulson@14335
  1323
val mem_Rep_preal_Ex = thm"mem_Rep_preal_Ex";
paulson@14335
  1324
val preal_add_commute = thm"preal_add_commute";
paulson@14335
  1325
val preal_add_assoc = thm"preal_add_assoc";
paulson@14335
  1326
val preal_add_left_commute = thm"preal_add_left_commute";
paulson@14335
  1327
val preal_mult_commute = thm"preal_mult_commute";
paulson@14335
  1328
val preal_mult_assoc = thm"preal_mult_assoc";
paulson@14335
  1329
val preal_mult_left_commute = thm"preal_mult_left_commute";
paulson@14335
  1330
val preal_add_mult_distrib2 = thm"preal_add_mult_distrib2";
paulson@14335
  1331
val preal_add_mult_distrib = thm"preal_add_mult_distrib";
paulson@14335
  1332
val preal_self_less_add_left = thm"preal_self_less_add_left";
paulson@14335
  1333
val preal_self_less_add_right = thm"preal_self_less_add_right";
paulson@14365
  1334
val less_add_left = thm"less_add_left";
paulson@14335
  1335
val preal_add_less2_mono1 = thm"preal_add_less2_mono1";
paulson@14335
  1336
val preal_add_less2_mono2 = thm"preal_add_less2_mono2";
paulson@14335
  1337
val preal_add_right_less_cancel = thm"preal_add_right_less_cancel";
paulson@14335
  1338
val preal_add_left_less_cancel = thm"preal_add_left_less_cancel";
paulson@14335
  1339
val preal_add_right_cancel = thm"preal_add_right_cancel";
paulson@14335
  1340
val preal_add_left_cancel = thm"preal_add_left_cancel";
paulson@14335
  1341
val preal_add_left_cancel_iff = thm"preal_add_left_cancel_iff";
paulson@14335
  1342
val preal_add_right_cancel_iff = thm"preal_add_right_cancel_iff";
paulson@14365
  1343
val preal_psup_le = thm"preal_psup_le";
paulson@14335
  1344
val psup_le_ub = thm"psup_le_ub";
paulson@14335
  1345
val preal_complete = thm"preal_complete";
paulson@14365
  1346
val preal_of_rat_add = thm"preal_of_rat_add";
paulson@14365
  1347
val preal_of_rat_mult = thm"preal_of_rat_mult";
paulson@14335
  1348
paulson@14335
  1349
val preal_add_ac = thms"preal_add_ac";
paulson@14335
  1350
val preal_mult_ac = thms"preal_mult_ac";
paulson@14335
  1351
*}
paulson@14335
  1352
paulson@5078
  1353
end