src/HOL/Quickcheck.thy
author haftmann
Fri Feb 05 14:33:50 2010 +0100 (2010-02-05)
changeset 35028 108662d50512
parent 34968 ceeffca32eb0
child 35880 2623b23e41fc
permissions -rw-r--r--
more consistent naming of type classes involving orderings (and lattices) -- c.f. NEWS
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(* Author: Florian Haftmann, TU Muenchen *)
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header {* A simple counterexample generator *}
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theory Quickcheck
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imports Random Code_Evaluation
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uses ("Tools/quickcheck_generators.ML")
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begin
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notation fcomp (infixl "o>" 60)
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notation scomp (infixl "o\<rightarrow>" 60)
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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 o\<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 random_itself :: "code_numeral \<Rightarrow> Random.seed \<Rightarrow> ('a itself \<times> (unit \<Rightarrow> term)) \<times> Random.seed" where
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  "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 chars o\<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 \<Rightarrow> (nat \<times> (unit \<Rightarrow> Code_Evaluation.term)) \<times> Random.seed" where
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  "random_nat i = Random.range (i + 1) o\<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) o\<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) \<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" where
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  "random_fun_lift f = random_fun_aux TYPEREP('a) TYPEREP('b) (op =) Code_Evaluation.term_of f Random.split_seed"
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instantiation "fun" :: ("{eq, term_of}", random) random
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begin
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definition random_fun :: "code_numeral \<Rightarrow> Random.seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> Random.seed" where
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  "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" where
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  "collapse f = (f o\<rightarrow> id)"
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definition beyond :: "code_numeral \<Rightarrow> code_numeral \<Rightarrow> code_numeral" where
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  "beyond k l = (if l > k then l else 0)"
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lemma beyond_zero:
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  "beyond k 0 = 0"
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  by (simp add: beyond_def)
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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 (Suc_code_numeral k) = rhs (Suc_code_numeral 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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use "Tools/quickcheck_generators.ML"
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setup Quickcheck_Generators.setup
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subsection {* Code setup *}
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code_const random_fun_aux (Quickcheck "Quickcheck'_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 Quickcheck_Generators
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no_notation fcomp (infixl "o>" 60)
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no_notation scomp (infixl "o\<rightarrow>" 60)
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subsection {* The Random-Predicate Monad *} 
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types 'a randompred = "Random.seed \<Rightarrow> ('a Predicate.pred \<times> Random.seed)"
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definition empty :: "'a randompred"
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  where "empty = Pair (bot_class.bot)"
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definition single :: "'a => 'a randompred"
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  where "single x = Pair (Predicate.single x)"
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definition bind :: "'a randompred \<Rightarrow> ('a \<Rightarrow> 'b randompred) \<Rightarrow> 'b randompred"
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  where
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    "bind R f = (\<lambda>s. let
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       (P, s') = R s;
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       (s1, s2) = Random.split_seed s'
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     in (Predicate.bind P (%a. fst (f a s1)), s2))"
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definition union :: "'a randompred \<Rightarrow> 'a randompred \<Rightarrow> 'a randompred"
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where
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  "union R1 R2 = (\<lambda>s. let
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     (P1, s') = R1 s; (P2, s'') = R2 s'
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   in (semilattice_sup_class.sup P1 P2, s''))"
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definition if_randompred :: "bool \<Rightarrow> unit randompred"
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where
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  "if_randompred b = (if b then single () else empty)"
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definition not_randompred :: "unit randompred \<Rightarrow> unit randompred"
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where
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  "not_randompred P = (\<lambda>s. let
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     (P', s') = P s
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   in if Predicate.eval P' () then (Orderings.bot, s') else (Predicate.single (), s'))"
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definition Random :: "(Random.seed \<Rightarrow> ('a \<times> (unit \<Rightarrow> term)) \<times> Random.seed) \<Rightarrow> 'a randompred"
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  where "Random g = scomp g (Pair o (Predicate.single o fst))"
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definition map :: "('a \<Rightarrow> 'b) \<Rightarrow> ('a randompred \<Rightarrow> 'b randompred)"
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  where "map f P = bind P (single o f)"
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hide (open) fact empty_def single_def bind_def union_def if_randompred_def not_randompred_def Random_def map_def
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hide (open) type randompred
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hide (open) const random collapse beyond random_fun_aux random_fun_lift
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  empty single bind union if_randompred not_randompred Random map
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end