(* Title: HOL/Quickcheck_Random.thy
Author: Florian Haftmann & Lukas Bulwahn, TU Muenchen
*)
section \<open>A simple counterexample generator performing random testing\<close>
theory Quickcheck_Random
imports Random Code_Evaluation Enum
begin
setup \<open>Code_Target.add_derived_target ("Quickcheck", [(Code_Runtime.target, I)])\<close>
subsection \<open>Catching Match exceptions\<close>
axiomatization catch_match :: "'a => 'a => 'a"
code_printing
constant catch_match \<rightharpoonup> (Quickcheck) "((_) handle Match => _)"
code_reserved Quickcheck Match
subsection \<open>The \<open>random\<close> class\<close>
class random = typerep +
fixes random :: "natural \ Random.seed \ ('a \ (unit \ term)) \ Random.seed"
subsection \<open>Fundamental and numeric types\<close>
instantiation bool :: random
begin
context
includes state_combinator_syntax
begin
definition
"random i = Random.range 2 \\
(\<lambda>k. Pair (if k = 0 then Code_Evaluation.valtermify False else Code_Evaluation.valtermify True))"
instance ..
end
end
instantiation itself :: (typerep) random
begin
definition
random_itself :: "natural \ Random.seed \ ('a itself \ (unit \ term)) \ Random.seed"
where "random_itself _ = Pair (Code_Evaluation.valtermify TYPE('a))"
instance ..
end
instantiation char :: random
begin
context
includes state_combinator_syntax
begin
definition
"random _ = Random.select (Enum.enum :: char list) \\ (\c. Pair (c, \u. Code_Evaluation.term_of c))"
instance ..
end
end
instantiation String.literal :: random
begin
definition
"random _ = Pair (STR '''', \u. Code_Evaluation.term_of (STR ''''))"
instance ..
end
instantiation nat :: random
begin
context
includes state_combinator_syntax
begin
definition random_nat :: "natural \ Random.seed
\<Rightarrow> (nat \<times> (unit \<Rightarrow> Code_Evaluation.term)) \<times> Random.seed"
where
"random_nat i = Random.range (i + 1) \\ (\k. Pair (
let n = nat_of_natural k
in (n, \<lambda>_. Code_Evaluation.term_of n)))"
instance ..
end
end
instantiation int :: random
begin
context
includes state_combinator_syntax
begin
definition
"random i = Random.range (2 * i + 1) \\ (\k. Pair (
let j = (if k \<ge> i then int (nat_of_natural (k - i)) else - (int (nat_of_natural (i - k))))
in (j, \<lambda>_. Code_Evaluation.term_of j)))"
instance ..
end
end
instantiation natural :: random
begin
context
includes state_combinator_syntax
begin
definition random_natural :: "natural \ Random.seed
\<Rightarrow> (natural \<times> (unit \<Rightarrow> Code_Evaluation.term)) \<times> Random.seed"
where
"random_natural i = Random.range (i + 1) \\ (\n. Pair (n, \_. Code_Evaluation.term_of n))"
instance ..
end
end
instantiation integer :: random
begin
context
includes state_combinator_syntax
begin
definition random_integer :: "natural \ Random.seed
\<Rightarrow> (integer \<times> (unit \<Rightarrow> Code_Evaluation.term)) \<times> Random.seed"
where
"random_integer i = Random.range (2 * i + 1) \\ (\k. Pair (
let j = (if k \<ge> i then integer_of_natural (k - i) else - (integer_of_natural (i - k)))
in (j, \<lambda>_. Code_Evaluation.term_of j)))"
instance ..
end
end
subsection \<open>Complex generators\<close>
text \<open>Towards \<^typ>\<open>'a \<Rightarrow> 'b\<close>\<close>
axiomatization random_fun_aux :: "typerep \ typerep \ ('a \ 'a \ bool) \ ('a \ term)
\<Rightarrow> (Random.seed \<Rightarrow> ('b \<times> (unit \<Rightarrow> term)) \<times> Random.seed)
\<Rightarrow> (Random.seed \<Rightarrow> Random.seed \<times> Random.seed)
\<Rightarrow> Random.seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
definition random_fun_lift :: "(Random.seed \ ('b \ (unit \ term)) \ Random.seed)
\<Rightarrow> Random.seed \<Rightarrow> (('a::term_of \<Rightarrow> 'b::typerep) \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
where
"random_fun_lift f =
random_fun_aux TYPEREP('a) TYPEREP('b) (=) Code_Evaluation.term_of f Random.split_seed"
instantiation "fun" :: ("{equal, term_of}", random) random
begin
definition
random_fun :: "natural \ Random.seed \ (('a \ 'b) \ (unit \ term)) \ Random.seed"
where "random i = random_fun_lift (random i)"
instance ..
end
text \<open>Towards type copies and datatypes\<close>
context
includes state_combinator_syntax
begin
definition collapse :: "('a \ ('a \ 'b \ 'a) \ 'a) \ 'a \ 'b \ 'a"
where "collapse f = (f \\ id)"
end
definition beyond :: "natural \ natural \ natural"
where "beyond k l = (if l > k then l else 0)"
lemma beyond_zero: "beyond k 0 = 0"
by (simp add: beyond_def)
context
includes term_syntax
begin
definition [code_unfold]:
"valterm_emptyset = Code_Evaluation.valtermify ({} :: ('a :: typerep) set)"
definition [code_unfold]:
"valtermify_insert x s = Code_Evaluation.valtermify insert {\} (x :: ('a :: typerep * _)) {\} s"
end
instantiation set :: (random) random
begin
context
includes state_combinator_syntax
begin
fun random_aux_set
where
"random_aux_set 0 j = collapse (Random.select_weight [(1, Pair valterm_emptyset)])"
| "random_aux_set (Code_Numeral.Suc i) j =
collapse (Random.select_weight
[(1, Pair valterm_emptyset),
(Code_Numeral.Suc i,
random j \<circ>\<rightarrow> (%x. random_aux_set i j \<circ>\<rightarrow> (%s. Pair (valtermify_insert x s))))])"
lemma [code]:
"random_aux_set i j =
collapse (Random.select_weight [(1, Pair valterm_emptyset),
(i, random j \<circ>\<rightarrow> (%x. random_aux_set (i - 1) j \<circ>\<rightarrow> (%s. Pair (valtermify_insert x s))))])"
proof (induct i rule: natural.induct)
case zero
show ?case by (subst select_weight_drop_zero [symmetric])
(simp add: random_aux_set.simps [simplified] less_natural_def)
next
case (Suc i)
show ?case by (simp only: random_aux_set.simps(2) [of "i"] Suc_natural_minus_one)
qed
definition "random_set i = random_aux_set i i"
instance ..
end
end
lemma random_aux_rec:
fixes random_aux :: "natural \ 'a"
assumes "random_aux 0 = rhs 0"
and "\k. random_aux (Code_Numeral.Suc k) = rhs (Code_Numeral.Suc k)"
shows "random_aux k = rhs k"
using assms by (rule natural.induct)
subsection \<open>Deriving random generators for datatypes\<close>
ML_file \<open>Tools/Quickcheck/quickcheck_common.ML\<close>
ML_file \<open>Tools/Quickcheck/random_generators.ML\<close>
subsection \<open>Code setup\<close>
code_printing
constant random_fun_aux \<rightharpoonup> (Quickcheck) "Random'_Generators.random'_fun"
\<comment> \<open>With enough criminal energy this can be abused to derive \<^prop>\<open>False\<close>;
for this reason we use a distinguished target \<open>Quickcheck\<close>
not spoiling the regular trusted code generation\<close>
code_reserved Quickcheck Random_Generators
hide_const (open) catch_match random collapse beyond random_fun_aux random_fun_lift
hide_fact (open) collapse_def beyond_def random_fun_lift_def
end
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