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(* Title: HOL/Library/Cancellation.thy
Author: Mathias Fleury, MPII
Copyright 2017
This theory defines cancelation simprocs that work on cancel_comm_monoid_add and support the simplification of an operation
that repeats the additions.
*)
theory Cancellation
imports Main
begin
named_theorems cancelation_simproc_pre \<open>These theorems are here to normalise the term. Special
handling of constructors should be here. Remark that only the simproc @{term NO_MATCH} is also
included.\<close>
named_theorems cancelation_simproc_post \<open>These theorems are here to normalise the term, after the
cancelation simproc. Normalisation of \<open>iterate_add\<close> back to the normale representation
should be put here.\<close>
named_theorems cancelation_simproc_eq_elim \<open>These theorems are here to help deriving contradiction
(e.g., \<open>Suc _ = 0\<close>).\<close>
definition iterate_add :: \<open>nat \<Rightarrow> 'a::cancel_comm_monoid_add \<Rightarrow> 'a\<close> where
\<open>iterate_add n a = (((+) a) ^^ n) 0\<close>
lemma iterate_add_simps[simp]:
\<open>iterate_add 0 a = 0\<close>
\<open>iterate_add (Suc n) a = a + iterate_add n a\<close>
unfolding iterate_add_def by auto
lemma iterate_add_empty[simp]: \<open>iterate_add n 0 = 0\<close>
unfolding iterate_add_def by (induction n) auto
lemma iterate_add_distrib[simp]: \<open>iterate_add (m+n) a = iterate_add m a + iterate_add n a\<close>
by (induction n) (auto simp: ac_simps)
lemma iterate_add_Numeral1: \<open>iterate_add n Numeral1 = of_nat n\<close>
by (induction n) auto
lemma iterate_add_1: \<open>iterate_add n 1 = of_nat n\<close>
using iterate_add_Numeral1 by auto
lemma iterate_add_eq_add_iff1:
\<open>i \<le> j \<Longrightarrow> (iterate_add j u + m = iterate_add i u + n) = (iterate_add (j - i) u + m = n)\<close>
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_eq_add_iff2:
\<open>i \<le> j \<Longrightarrow> (iterate_add i u + m = iterate_add j u + n) = (m = iterate_add (j - i) u + n)\<close>
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_less_iff1:
"j \ (i::nat) \ (iterate_add i (u:: 'a :: {cancel_comm_monoid_add, ordered_ab_semigroup_add_imp_le}) + m < iterate_add j u + n) = (iterate_add (i-j) u + m < n)"
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_less_iff2:
"i \ (j::nat) \ (iterate_add i (u:: 'a :: {cancel_comm_monoid_add, ordered_ab_semigroup_add_imp_le}) + m < iterate_add j u + n) = (m
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_less_eq_iff1:
"j \ (i::nat) \ (iterate_add i (u:: 'a :: {cancel_comm_monoid_add, ordered_ab_semigroup_add_imp_le}) + m \ iterate_add j u + n) = (iterate_add (i-j) u + m \ n)"
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_less_eq_iff2:
"i \ (j::nat) \ (iterate_add i (u:: 'a :: {cancel_comm_monoid_add, ordered_ab_semigroup_add_imp_le}) + m \ iterate_add j u + n) = (m \ iterate_add (j - i) u + n)"
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_add_eq1:
"j \ (i::nat) \ ((iterate_add i u + m) - (iterate_add j u + n)) = ((iterate_add (i-j) u + m) - n)"
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
lemma iterate_add_diff_add_eq2:
"i \ (j::nat) \ ((iterate_add i u + m) - (iterate_add j u + n)) = (m - (iterate_add (j-i) u + n))"
by (auto dest!: le_Suc_ex add_right_imp_eq simp: ab_semigroup_add_class.add_ac(1))
subsection \<open>Simproc Set-Up\<close>
ML_file \<open>Cancellation/cancel.ML\<close>
ML_file \<open>Cancellation/cancel_data.ML\<close>
ML_file \<open>Cancellation/cancel_simprocs.ML\<close>
end
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