theory Simps_Case_Conv_Examples imports
"HOL-Library.Simps_Case_Conv"
begin
section \<open>Tests for the Simps<->Case conversion tools\<close>
fun foo where
"foo (x # xs) Nil = 0" |
"foo (x # xs) (y # ys) = foo [] []" |
"foo Nil (y # ys) = 1" |
"foo Nil Nil = 3"
fun bar where
"bar x 0 y = 0 + x" |
"bar x (Suc n) y = n + x"
definition
split_rule_test :: "((nat => 'a) + ('b * (('b => 'a) option))) => ('a => nat) => nat"
where
"split_rule_test x f = f (case x of Inl af \<Rightarrow> af 1
| Inr (b, None) => inv f 0
| Inr (b, Some g) => g b)"
definition test where "test x y = (case x of None => (case y of [] => 1 | _ # _ => 2) | Some x => x)"
definition nosplit where "nosplit x = x @ (case x of [] \<Rightarrow> [1] | xs \<Rightarrow> xs)"
text \<open>Function with complete, non-overlapping patterns\<close>
case_of_simps foo_cases1: foo.simps
lemma
fixes xs :: "'a list" and ys :: "'b list"
shows "foo xs ys =
(case xs of [] \<Rightarrow> (case ys of [] \<Rightarrow> 3 | _ # _ \<Rightarrow> 1)
| _ # _ \<Rightarrow> (case ys of [] \<Rightarrow> 0 | _ # _ \<Rightarrow> foo ([] :: 'a list) ([] :: 'b list)))"
by (fact foo_cases1)
text \<open>Redundant equations are ignored\<close>
case_of_simps foo_cases2: foo.simps foo.simps
lemma
fixes xs :: "'a list" and ys :: "'b list"
shows "foo xs ys =
(case xs of [] \<Rightarrow> (case ys of [] \<Rightarrow> 3 | _ # _ \<Rightarrow> 1)
| _ # _ \<Rightarrow> (case ys of [] \<Rightarrow> 0 | _ # _ \<Rightarrow> foo ([] :: 'a list) ([] :: 'b list)))"
by (fact foo_cases2)
text \<open>Variable patterns\<close>
case_of_simps bar_cases: bar.simps
lemma "bar x n y = (case n of 0 \<Rightarrow> 0 + x | Suc n' \<Rightarrow> n' + x)" by(fact bar_cases)
text \<open>Case expression not at top level\<close>
simps_of_case split_rule_test_simps: split_rule_test_def
lemma
"split_rule_test (Inl x) f = f (x 1)"
"split_rule_test (Inr (x, None)) f = f (inv f 0)"
"split_rule_test (Inr (x, Some y)) f = f (y x)"
by (fact split_rule_test_simps)+
text \<open>Argument occurs both as case parameter and seperately\<close>
simps_of_case nosplit_simps1: nosplit_def
lemma
"nosplit [] = [] @ [1]"
"nosplit (x # xs) = (x # xs) @ x # xs"
by (fact nosplit_simps1)+
text \<open>Nested case expressions\<close>
simps_of_case test_simps1: test_def
lemma
"test None [] = 1"
"test None (x # xs) = 2"
"test (Some x) y = x"
by (fact test_simps1)+
text \<open>Single-constructor patterns\<close>
case_of_simps fst_conv_simps: fst_conv
lemma "fst x = (case x of (a,b) \<Rightarrow> a)"
by (fact fst_conv_simps)
text \<open>Partial split of case\<close>
simps_of_case nosplit_simps2: nosplit_def (splits: list.split)
lemma
"nosplit [] = [] @ [1]"
"nosplit (x # xs) = (x # xs) @ x # xs"
by (fact nosplit_simps1)+
simps_of_case test_simps2: test_def (splits: option.split)
lemma
"test None y = (case y of [] \<Rightarrow> 1 | x # xs \<Rightarrow> 2)"
"test (Some x) y = x"
by (fact test_simps2)+
text \<open>Reversal\<close>
case_of_simps test_def1: test_simps1
lemma
"test x y =
(case x of None \<Rightarrow> (case y of [] \<Rightarrow> 1 | _ # _ \<Rightarrow> 2)
| Some x' \<Rightarrow> x')"
by (fact test_def1)
text \<open>Case expressions on RHS\<close>
case_of_simps test_def2: test_simps2
lemma "test x y =
(case x of None \<Rightarrow> (case y of [] \<Rightarrow> 1 | _ # _ \<Rightarrow> 2)
| Some x' \<Rightarrow> x')"
by (fact test_def2)
text \<open>Partial split of simps\<close>
case_of_simps foo_cons_def: foo.simps(1,2)
lemma
fixes xs :: "'a list" and ys :: "'b list"
shows "foo (x # xs) ys = (case ys of [] \<Rightarrow> 0 | _ # _ \<Rightarrow> foo ([] :: 'a list) ([] :: 'b list))"
by (fact foo_cons_def)
end