src/HOL/Quickcheck_Random.thy
author haftmann
Thu Feb 14 15:27:10 2013 +0100 (2013-02-14)
changeset 51126 df86080de4cb
parent 50046 src/HOL/Quickcheck.thy@0051dc4f301f
child 51143 0a2371e7ced3
permissions -rw-r--r--
reform of predicate compiler / quickcheck theories:
implement yieldn operations uniformly on the ML level -- predicate compiler uses negative integers as parameter to yieldn, whereas code_numeral represents natural numbers!
avoid odd New_ prefix by joining related theories;
avoid overcompact name DSequence;
separated predicate inside random monad into separate theory;
consolidated name of theory Quickcheck
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(* Author: Florian Haftmann & Lukas Bulwahn, TU Muenchen *)
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header {* A simple counterexample generator performing random testing *}
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theory Quickcheck_Random
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imports Random Code_Evaluation Enum
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begin
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notation fcomp (infixl "\<circ>>" 60)
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notation scomp (infixl "\<circ>\<rightarrow>" 60)
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setup {* Code_Target.extend_target ("Quickcheck", (Code_Runtime.target, K I)) *}
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subsection {* Catching Match exceptions *}
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axiomatization catch_match :: "'a => 'a => 'a"
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code_const catch_match 
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  (Quickcheck "((_) handle Match => _)")
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subsection {* The @{text random} class *}
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class random = typerep +
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  fixes random :: "code_numeral \<Rightarrow> Random.seed \<Rightarrow> ('a \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
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subsection {* Fundamental and numeric types*}
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instantiation bool :: random
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begin
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definition
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  "random i = Random.range 2 \<circ>\<rightarrow>
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    (\<lambda>k. Pair (if k = 0 then Code_Evaluation.valtermify False else Code_Evaluation.valtermify True))"
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instance ..
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end
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instantiation itself :: (typerep) random
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begin
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definition
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  random_itself :: "code_numeral \<Rightarrow> Random.seed \<Rightarrow> ('a itself \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
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where "random_itself _ = Pair (Code_Evaluation.valtermify TYPE('a))"
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instance ..
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end
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instantiation char :: random
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begin
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definition
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  "random _ = Random.select (Enum.enum :: char list) \<circ>\<rightarrow> (\<lambda>c. Pair (c, \<lambda>u. Code_Evaluation.term_of c))"
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instance ..
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end
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instantiation String.literal :: random
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begin
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definition 
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  "random _ = Pair (STR '''', \<lambda>u. Code_Evaluation.term_of (STR ''''))"
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instance ..
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end
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instantiation nat :: random
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begin
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definition random_nat :: "code_numeral \<Rightarrow> Random.seed
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  \<Rightarrow> (nat \<times> (unit \<Rightarrow> Code_Evaluation.term)) \<times> Random.seed"
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where
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  "random_nat i = Random.range (i + 1) \<circ>\<rightarrow> (\<lambda>k. Pair (
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     let n = Code_Numeral.nat_of k
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     in (n, \<lambda>_. Code_Evaluation.term_of n)))"
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instance ..
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end
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instantiation int :: random
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begin
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definition
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  "random i = Random.range (2 * i + 1) \<circ>\<rightarrow> (\<lambda>k. Pair (
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     let j = (if k \<ge> i then Code_Numeral.int_of (k - i) else - Code_Numeral.int_of (i - k))
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     in (j, \<lambda>_. Code_Evaluation.term_of j)))"
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instance ..
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end
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subsection {* Complex generators *}
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text {* Towards @{typ "'a \<Rightarrow> 'b"} *}
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axiomatization random_fun_aux :: "typerep \<Rightarrow> typerep \<Rightarrow> ('a \<Rightarrow> 'a \<Rightarrow> bool) \<Rightarrow> ('a \<Rightarrow> term)
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  \<Rightarrow> (Random.seed \<Rightarrow> ('b \<times> (unit \<Rightarrow> term)) \<times> Random.seed)
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  \<Rightarrow> (Random.seed \<Rightarrow> Random.seed \<times> Random.seed)
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  \<Rightarrow> Random.seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
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definition random_fun_lift :: "(Random.seed \<Rightarrow> ('b \<times> (unit \<Rightarrow> term)) \<times> Random.seed)
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  \<Rightarrow> Random.seed \<Rightarrow> (('a\<Colon>term_of \<Rightarrow> 'b\<Colon>typerep) \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
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where
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  "random_fun_lift f =
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    random_fun_aux TYPEREP('a) TYPEREP('b) (op =) Code_Evaluation.term_of f Random.split_seed"
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instantiation "fun" :: ("{equal, term_of}", random) random
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begin
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definition
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  random_fun :: "code_numeral \<Rightarrow> Random.seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> Random.seed"
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  where "random i = random_fun_lift (random i)"
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instance ..
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end
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text {* Towards type copies and datatypes *}
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definition collapse :: "('a \<Rightarrow> ('a \<Rightarrow> 'b \<times> 'a) \<times> 'a) \<Rightarrow> 'a \<Rightarrow> 'b \<times> 'a"
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  where "collapse f = (f \<circ>\<rightarrow> id)"
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definition beyond :: "code_numeral \<Rightarrow> code_numeral \<Rightarrow> code_numeral"
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  where "beyond k l = (if l > k then l else 0)"
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lemma beyond_zero: "beyond k 0 = 0"
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  by (simp add: beyond_def)
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definition (in term_syntax) [code_unfold]:
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  "valterm_emptyset = Code_Evaluation.valtermify ({} :: ('a :: typerep) set)"
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definition (in term_syntax) [code_unfold]:
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  "valtermify_insert x s = Code_Evaluation.valtermify insert {\<cdot>} (x :: ('a :: typerep * _)) {\<cdot>} s"
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instantiation set :: (random) random
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begin
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primrec random_aux_set
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where
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  "random_aux_set 0 j = collapse (Random.select_weight [(1, Pair valterm_emptyset)])"
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| "random_aux_set (Code_Numeral.Suc i) j =
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    collapse (Random.select_weight
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      [(1, Pair valterm_emptyset),
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       (Code_Numeral.Suc i,
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        random j \<circ>\<rightarrow> (%x. random_aux_set i j \<circ>\<rightarrow> (%s. Pair (valtermify_insert x s))))])"
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lemma [code]:
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  "random_aux_set i j =
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    collapse (Random.select_weight [(1, Pair valterm_emptyset),
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      (i, random j \<circ>\<rightarrow> (%x. random_aux_set (i - 1) j \<circ>\<rightarrow> (%s. Pair (valtermify_insert x s))))])"
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proof (induct i rule: code_numeral.induct)
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  case zero
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  show ?case by (subst select_weight_drop_zero [symmetric])
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    (simp add: random_aux_set.simps [simplified])
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next
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  case (Suc i)
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  show ?case by (simp only: random_aux_set.simps(2) [of "i"] Suc_code_numeral_minus_one)
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qed
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definition "random_set i = random_aux_set i i"
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instance ..
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end
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lemma random_aux_rec:
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  fixes random_aux :: "code_numeral \<Rightarrow> 'a"
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  assumes "random_aux 0 = rhs 0"
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    and "\<And>k. random_aux (Code_Numeral.Suc k) = rhs (Code_Numeral.Suc k)"
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  shows "random_aux k = rhs k"
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  using assms by (rule code_numeral.induct)
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subsection {* Deriving random generators for datatypes *}
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ML_file "Tools/Quickcheck/quickcheck_common.ML" 
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ML_file "Tools/Quickcheck/random_generators.ML"
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setup Random_Generators.setup
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subsection {* Code setup *}
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code_const random_fun_aux (Quickcheck "Random'_Generators.random'_fun")
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  -- {* With enough criminal energy this can be abused to derive @{prop False};
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  for this reason we use a distinguished target @{text Quickcheck}
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  not spoiling the regular trusted code generation *}
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code_reserved Quickcheck Random_Generators
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no_notation fcomp (infixl "\<circ>>" 60)
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no_notation scomp (infixl "\<circ>\<rightarrow>" 60)
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hide_const (open) catch_match random collapse beyond random_fun_aux random_fun_lift
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hide_fact (open) collapse_def beyond_def random_fun_lift_def
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end
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