(* Title: HOL/Library/Char_ord.thy
ID: $Id$
Author: Norbert Voelker, Florian Haftmann
*)
header {* Order on characters *}
theory Char_ord
imports Product_ord Char_nat
begin
instance nibble :: linorder
nibble_less_eq_def: "n \<le> m \<equiv> nat_of_nibble n \<le> nat_of_nibble m"
nibble_less_def: "n < m \<equiv> nat_of_nibble n < nat_of_nibble m"
proof
fix n :: nibble show "n \<le> n" unfolding nibble_less_eq_def nibble_less_def by auto
next
fix n m q :: nibble
assume "n \<le> m"
and "m \<le> q"
then show "n \<le> q" unfolding nibble_less_eq_def nibble_less_def by auto
next
fix n m :: nibble
assume "n \<le> m"
and "m \<le> n"
then show "n = m" unfolding nibble_less_eq_def nibble_less_def by (auto simp add: nat_of_nibble_eq)
next
fix n m :: nibble
show "n < m \<longleftrightarrow> n \<le> m \<and> n \<noteq> m"
unfolding nibble_less_eq_def nibble_less_def less_le by (auto simp add: nat_of_nibble_eq)
next
fix n m :: nibble
show "n \<le> m \<or> m \<le> n"
unfolding nibble_less_eq_def by auto
qed
instance nibble :: distrib_lattice
"inf \<equiv> min"
"sup \<equiv> max"
by default
(auto simp add: inf_nibble_def sup_nibble_def min_max.sup_inf_distrib1)
instance char :: linorder
char_less_eq_def: "c1 \<le> c2 \<equiv> case c1 of Char n1 m1 \<Rightarrow> case c2 of Char n2 m2 \<Rightarrow>
n1 < n2 \<or> n1 = n2 \<and> m1 \<le> m2"
char_less_def: "c1 < c2 \<equiv> case c1 of Char n1 m1 \<Rightarrow> case c2 of Char n2 m2 \<Rightarrow>
n1 < n2 \<or> n1 = n2 \<and> m1 < m2"
by default (auto simp: char_less_eq_def char_less_def split: char.splits)
lemmas [code func del] = char_less_eq_def char_less_def
instance char :: distrib_lattice
"inf \<equiv> min"
"sup \<equiv> max"
by default
(auto simp add: inf_char_def sup_char_def min_max.sup_inf_distrib1)
lemma [simp, code func]:
shows char_less_eq_simp: "Char n1 m1 \<le> Char n2 m2 \<longleftrightarrow> n1 < n2 \<or> n1 = n2 \<and> m1 \<le> m2"
and char_less_simp: "Char n1 m1 < Char n2 m2 \<longleftrightarrow> n1 < n2 \<or> n1 = n2 \<and> m1 < m2"
unfolding char_less_eq_def char_less_def by simp_all
end