Test.LeanCheck.Utils.TypeBinding

This module is part of LeanCheck, a simple enumerative property-based testing library.

Infix operators for type binding using dummy first-class values.

Those are useful when property based testing to avoid repetition. Suppose:

prop_sortAppend :: Ord a => [a] -> Bool
prop_sortAppend xs =  sort (xs++ys) == sort (ys++xs)

Then this:

testResults n =
  [ holds n (prop_sortAppend :: [Int] -> [Int] -> Bool)
  , holds n (prop_sortAppend :: [UInt2] -> [UInt2] -> Bool)
  , holds n (prop_sortAppend :: [Bool] -> [Bool] -> Bool)
  , holds n (prop_sortAppend :: [Char] -> [Char] -> Bool)
  , holds n (prop_sortAppend :: [String] -> [String] -> Bool)
  , holds n (prop_sortAppend :: [()] -> [()] -> Bool)
  ]

Becomes this:

testResults n =
  [ holds n $ prop_sortAppend -:> [int]
  , holds n $ prop_sortAppend -:> [uint2]
  , holds n $ prop_sortAppend -:> [bool]
  , holds n $ prop_sortAppend -:> [char]
  , holds n $ prop_sortAppend -:> [string]
  , holds n $ prop_sortAppend -:> [()]
  ]

Or even:

testResults n = concat
  [ for int, for uint2, for bool, for (), for char, for string ]
  where for a = [ holds n $ prop_sortAppend -:> a ]

This last form is useful when testing multiple properties for multiple types.

Type binding operators

Summary:

• as type of: -:
• argument as type of: -:>
• result as type of: ->:
• second argument as type of: ->:>
• second result as type of: ->>:
• third argument as type of: ->>:>
• third result as type of: ->>>:

(-:) :: a -> a -> a infixl 1

Type restricted version of const that forces its first argument to have the same type as the second. A symnonym to asTypeOf:

 value -: ty  =  value :: Ty

Examples:

 10 -: int   =  10 :: Int
 undefined -: 'a' >- 'b'  =  undefined :: Char -> Char

(-:>) :: (a -> b) -> a -> a -> b infixl 1

Type restricted version of const that forces the argument of its first argument to have the same type as the second:

 f -:> ty  =  f -: ty >- und  =  f :: Ty -> a

Example:

 abs -:> int   =  abs -: int >- und  =  abs :: Int -> Int

(->:) :: (a -> b) -> b -> a -> b infixl 1

Type restricted version of const that forces the result of its first argument to have the same type as the second.

 f ->: ty  =  f -: und >- ty  =  f :: a -> Ty

(->:>) :: (a -> b -> c) -> b -> a -> b -> c infixl 1

Type restricted version of const that forces the second argument of its first argument to have the same type as the second.

f ->:> ty   =  f -: und -> ty -> und  =  f :: a -> Ty -> b

(->>:) :: (a -> b -> c) -> c -> a -> b -> c infixl 1

Type restricted version of const that forces the result of the result of its first argument to have the same type as the second.

f ->>: ty   =  f -: und -> und -> ty  =  f :: a -> b -> Ty

(->>:>) :: (a -> b -> c -> d) -> c -> a -> b -> c -> d infixl 1

Type restricted version of const that forces the third argument of its first argument to have the same type as the second.

(->>>:) :: (a -> b -> c -> d) -> d -> a -> b -> c -> d infixl 1

Type restricted version of const that forces the result of the result of the result of its first argument to have the same type as the second.

(->>>:>) :: (a -> b -> c -> d -> e) -> d -> a -> b -> c -> d -> e infixl 1

(->>>>:) :: (a -> b -> c -> d -> e) -> e -> a -> b -> c -> d -> e infixl 1

(->>>>:>) :: (a -> b -> c -> d -> e -> f) -> e -> a -> b -> c -> d -> e -> f infixl 1

(->>>>>:) :: (a -> b -> c -> d -> e -> f) -> f -> a -> b -> c -> d -> e -> f infixl 1

(->>>>>:>) :: (a -> b -> c -> d -> e -> f -> g) -> f -> a -> b -> c -> d -> e -> f -> g infixl 1

(->>>>>>:) :: (a -> b -> c -> d -> e -> f -> g) -> g -> a -> b -> c -> d -> e -> f -> g infixl 1

(->>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h) -> g -> a -> b -> c -> d -> e -> f -> g -> h infixl 1

(->>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h) -> h -> a -> b -> c -> d -> e -> f -> g -> h infixl 1

(->>>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h -> i) -> h -> a -> b -> c -> d -> e -> f -> g -> h -> i infixl 1

(->>>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h -> i) -> i -> a -> b -> c -> d -> e -> f -> g -> h -> i infixl 1

(->>>>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j) -> i -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j infixl 1

(->>>>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j) -> j -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j infixl 1

(->>>>>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k) -> j -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k infixl 1

(->>>>>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k) -> k -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k infixl 1

(->>>>>>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l) -> k -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l infixl 1

(->>>>>>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l) -> l -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l infixl 1

(->>>>>>>>>>>:>) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l -> m) -> m -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l -> m infixl 1

(->>>>>>>>>>>>:) :: (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l -> m) -> m -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k -> l -> m infixl 1

Dummy (undefined) values

Standard Haskell types

und :: a

Shorthand for undefined

(>-) :: a -> b -> a -> b infixr 9

Returns an undefined functional value that takes an argument of the type of its first argument and return a value of the type of its second argument.

ty >- ty  =  (undefined :: Ty -> Ty)

Examples:

'a' >- 'b'  =  char >- char  =  (undefined :: Char -> Char)
int >- bool >- int  =  undefined :: Int -> Bool -> Int

bool :: Bool

int :: Int

integer :: Integer

float :: Float

double :: Double

char :: Char

string :: String

ordering :: Ordering

mayb :: a -> Maybe a

It might be better to just use Just

eith :: a -> b -> Either a b

Testing types

nat :: Nat

int1 :: Int1

uint1 :: UInt1

int2 :: Int2

uint2 :: UInt2

int3 :: Int3

uint3 :: UInt3

int4 :: Int4

uint4 :: UInt4