(* Title: HOL/Semiring_Normalization.thy
Author: Amine Chaieb, TU Muenchen
*)
section {* Semiring normalization *}
theory Semiring_Normalization
imports Numeral_Simprocs Nat_Transfer
begin
text {* Prelude *}
class comm_semiring_1_cancel_crossproduct = comm_semiring_1_cancel +
assumes crossproduct_eq: "w * y + x * z = w * z + x * y \<longleftrightarrow> w = x \<or> y = z"
begin
lemma crossproduct_noteq:
"a \<noteq> b \<and> c \<noteq> d \<longleftrightarrow> a * c + b * d \<noteq> a * d + b * c"
by (simp add: crossproduct_eq)
lemma add_scale_eq_noteq:
"r \<noteq> 0 \<Longrightarrow> a = b \<and> c \<noteq> d \<Longrightarrow> a + r * c \<noteq> b + r * d"
proof (rule notI)
assume nz: "r\<noteq> 0" and cnd: "a = b \<and> c\<noteq>d"
and eq: "a + (r * c) = b + (r * d)"
have "(0 * d) + (r * c) = (0 * c) + (r * d)"
using add_left_imp_eq eq mult_zero_left by (simp add: cnd)
then show False using crossproduct_eq [of 0 d] nz cnd by simp
qed
lemma add_0_iff:
"b = b + a \<longleftrightarrow> a = 0"
using add_left_imp_eq [of b a 0] by auto
end
subclass (in idom) comm_semiring_1_cancel_crossproduct
proof
fix w x y z
show "w * y + x * z = w * z + x * y \<longleftrightarrow> w = x \<or> y = z"
proof
assume "w * y + x * z = w * z + x * y"
then have "w * y + x * z - w * z - x * y = 0" by (simp add: algebra_simps)
then have "w * (y - z) - x * (y - z) = 0" by (simp add: algebra_simps)
then have "(y - z) * (w - x) = 0" by (simp add: algebra_simps)
then have "y - z = 0 \<or> w - x = 0" by (rule divisors_zero)
then show "w = x \<or> y = z" by auto
qed (auto simp add: ac_simps)
qed
instance nat :: comm_semiring_1_cancel_crossproduct
proof
fix w x y z :: nat
have aux: "\<And>y z. y < z \<Longrightarrow> w * y + x * z = w * z + x * y \<Longrightarrow> w = x"
proof -
fix y z :: nat
assume "y < z" then have "\<exists>k. z = y + k \<and> k \<noteq> 0" by (intro exI [of _ "z - y"]) auto
then obtain k where "z = y + k" and "k \<noteq> 0" by blast
assume "w * y + x * z = w * z + x * y"
then have "(w * y + x * y) + x * k = (w * y + x * y) + w * k" by (simp add: `z = y + k` algebra_simps)
then have "x * k = w * k" by simp
then show "w = x" using `k \<noteq> 0` by simp
qed
show "w * y + x * z = w * z + x * y \<longleftrightarrow> w = x \<or> y = z"
by (auto simp add: neq_iff dest!: aux)
qed
text {* Semiring normalization proper *}
ML_file "Tools/semiring_normalizer.ML"
context comm_semiring_1
begin
declaration \<open>
let
val rules = @{lemma
"(a * m) + (b * m) = (a + b) * m"
"(a * m) + m = (a + 1) * m"
"m + (a * m) = (a + 1) * m"
"m + m = (1 + 1) * m"
"0 + a = a"
"a + 0 = a"
"a * b = b * a"
"(a + b) * c = (a * c) + (b * c)"
"0 * a = 0"
"a * 0 = 0"
"1 * a = a"
"a * 1 = a"
"(lx * ly) * (rx * ry) = (lx * rx) * (ly * ry)"
"(lx * ly) * (rx * ry) = lx * (ly * (rx * ry))"
"(lx * ly) * (rx * ry) = rx * ((lx * ly) * ry)"
"(lx * ly) * rx = (lx * rx) * ly"
"(lx * ly) * rx = lx * (ly * rx)"
"lx * (rx * ry) = (lx * rx) * ry"
"lx * (rx * ry) = rx * (lx * ry)"
"(a + b) + (c + d) = (a + c) + (b + d)"
"(a + b) + c = a + (b + c)"
"a + (c + d) = c + (a + d)"
"(a + b) + c = (a + c) + b"
"a + c = c + a"
"a + (c + d) = (a + c) + d"
"(x ^ p) * (x ^ q) = x ^ (p + q)"
"x * (x ^ q) = x ^ (Suc q)"
"(x ^ q) * x = x ^ (Suc q)"
"x * x = x\<^sup>2"
"(x * y) ^ q = (x ^ q) * (y ^ q)"
"(x ^ p) ^ q = x ^ (p * q)"
"x ^ 0 = 1"
"x ^ 1 = x"
"x * (y + z) = (x * y) + (x * z)"
"x ^ (Suc q) = x * (x ^ q)"
"x ^ (2*n) = (x ^ n) * (x ^ n)"
by (simp_all add: algebra_simps power_add power2_eq_square
power_mult_distrib power_mult del: one_add_one)}
in
Semiring_Normalizer.declare @{thm comm_semiring_1_axioms}
{semiring = ([@{cpat "?x + ?y"}, @{cpat "?x * ?y"}, @{cpat "?x ^ ?n"}, @{cpat 0}, @{cpat 1}],
rules), ring = ([], []), field = ([], []), idom = [], ideal = []}
end\<close>
end
context comm_ring_1
begin
declaration \<open>
let
val rules = @{lemma
"- x = (- 1) * x"
"x - y = x + (- y)"
by simp_all}
in
Semiring_Normalizer.declare @{thm comm_ring_1_axioms}
{semiring = Semiring_Normalizer.the_semiring @{context} @{thm comm_semiring_1_axioms},
ring = ([@{cpat "?x - ?y"}, @{cpat "- ?x"}], rules), field = ([], []), idom = [], ideal = []}
end\<close>
end
context comm_semiring_1_cancel_crossproduct
begin
declaration \<open>Semiring_Normalizer.declare @{thm comm_semiring_1_cancel_crossproduct_axioms}
{semiring = Semiring_Normalizer.the_semiring @{context} @{thm comm_semiring_1_axioms},
ring = ([], []), field = ([], []), idom = @{thms crossproduct_noteq add_scale_eq_noteq}, ideal = []}\<close>
end
context idom
begin
declaration \<open>Semiring_Normalizer.declare @{thm idom_axioms}
{semiring = Semiring_Normalizer.the_semiring @{context} @{thm comm_ring_1_axioms},
ring = Semiring_Normalizer.the_ring @{context} @{thm comm_ring_1_axioms},
field = ([], []), idom = @{thms crossproduct_noteq add_scale_eq_noteq},
ideal = @{thms right_minus_eq add_0_iff}}\<close>
end
context field
begin
declaration \<open>Semiring_Normalizer.declare @{thm field_axioms}
{semiring = Semiring_Normalizer.the_semiring @{context} @{thm idom_axioms},
ring = Semiring_Normalizer.the_ring @{context} @{thm idom_axioms},
field = ([@{cpat "?x / ?y"}, @{cpat "inverse ?x"}], @{thms divide_inverse inverse_eq_divide}),
idom = Semiring_Normalizer.the_idom @{context} @{thm idom_axioms},
ideal = Semiring_Normalizer.the_ideal @{context} @{thm idom_axioms}}\<close>
end
code_identifier
code_module Semiring_Normalization \<rightharpoonup> (SML) Arith and (OCaml) Arith and (Haskell) Arith
end