codo-notation

A notation for comonads, analogous to the do-notation for monads.

A notation for comonads, analogous to the do-notation for monads.

Requires the TemplateHaskell and QuasiQuotes extensions.

Example 1:

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE QuasiQuotes #-}

import Control.Comonad
import Language.Haskell.Codo

foo :: (Comonad c, Num a) => c a -> a
foo = [codo| x => extract x + 1 |]

Example 2:

import Data.Monoid
instance Monoid Double where
       mempty = 0.0
       mappend = (+)

differentiate f = ((f 0.001) - f 0) / 0.001

minima :: (Double -> Double) -> Bool
minima = [codo| f => f'  <- differentiate f
                     f'' <- differentiate f'
                     (extract f' < 0.001) && (extract f'' > 0) |]

Further explanation of the syntax can be found in the following (short) paper: http://www.cl.cam.ac.uk/~dao29/drafts/codo-notation-orchard-ifl12.pdf with a numer of examples.

Further examples can be found here: https://github.com/dorchard/codo-notation.