Copyright | (c) 2015-2020 Rudy Matela |
---|---|

License | 3-Clause BSD (see the file LICENSE) |

Maintainer | Rudy Matela <rudy@matela.com.br> |

Safe Haskell | None |

Language | Haskell2010 |

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

This module exports an orphan `Show`

instance for functions.
It shows functions as up to 8 case distinctions, one per line.

*Warning: this is only intended to be used in testing modules.*
*Avoid importing this on modules that are used as libraries.*

This is intended to `Show`

functions
generated by the `Listable`

instance for functions
defined in Test.LeanCheck.Function.Listable:
functions that have finite exceptions to a constant function.
It does work on other types of functions, albeit using `"..."`

.

> print (&&) \x y -> case (x,y) of (True,True) -> True _ -> False

> print (==>) \x y -> case (x,y) of (True,False) -> False _ -> True

> print (==2) \x -> case x of 2 -> True _ -> False

> print (\x -> abs x < 2) \x -> case x of 0 -> True 1 -> True -1 -> True _ -> False

When the function cannot be defined by finite exceptions to a constant
function using 8 case-patterns, the rest of the function is represented by
`"..."`

.

> print (+) \x y -> case (x,y) of (0,0) -> 0 (0,1) -> 1 (1,0) -> 1 (0,-1) -> -1 (1,1) -> 2 (-1,0) -> -1 (0,2) -> 2 (1,-1) -> 0 ...

The exported orphan `Show`

`->`

instance is actually defined in
Test.LeanCheck.Function.Show.EightLines. An alternative is provided in
Test.LeanCheck.Function.Show.FourCases.

The exported `Show`

instance only works for functions whose ultimate return
types are instances of `ShowFunction`

.
For user-defined algebraic datatypes that are instances of `Show`

, their
ShowFunction instance can be defined by using
`bindtiersShow`

:

import Test.LeanCheck.Function.ShowFunction instance ShowFunction Ty where bindtiers = bindtiersShow