Pointless Lenses
This cabal package can be installed with:
$ cabal install pointless-lenses
For a manual install, execute:
$ runhaskell Setup.lhs configure
$ runhaskell Setup.lhs build
$ runhaskell Setup.lhs install
You can now start playing with the example code that comes with the library, under Language.Pointless.Examples.Examples.
The easiest way is to create a new module that imports some library modules
module Test where
import Test.QuickCheck.Test
import Generics.Pointless.Lenses
import Generics.Pointless.Lenses.Examples.Examples
and interpret it
$ ghci Test.hs
We can now test the well-behavedness of some lens, for example:
> quickCheck (wb filter_left_lns)
+++ OK, passed 100 tests.
Or run some example and later check what it is actually doing:
> put filter_left_lns ([1,2,3],[Left 0,Right 'a',Left 4])
[Left 1,Right 'a',Left 2,Left 3]