lambda-fairy

TODO

• Exceptions
• Delimited continuations, because continuations are cool.
• Macros (maybe)
• Attribute lookup – lenses?
• Keyword parameters
  • [GHC implicit parameters][] are interesting

lambda-fairy

-- | Birthday paradox calculator

import Control.Monad
import Data.Ratio
import System.Environment
import Text.Printf

birthday :: Fractional a => Integer -> Integer -> a
birthday days n = realToFrac $ 1 - inverse
  where

lambda-fairy

javascript:
var frm = window.frames[2];
function next(f) {
    setTimeout(f, 100);
}
function doClick(elem) {
    var evt = document.createEvent("MouseEvents");
    evt.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
    elem.dispatchEvent(evt);
}

lambda-fairy

import qualified Control.Exception.Lifted as Lifted
import Control.Monad.Trans.Control

-- | Set an option, run an action, then restore the option to its
-- previous value.
--
-- @saveRestore get set value action@ is roughly equivalent to:
--
-- > do orig <- get
-- >    set value

lambda-fairy

-- | Lock-step folding.
--
-- This module presents an elegant way of executing multiple left folds
-- on one list using constant memory. For example, the mean can be
-- expressed as:
--
-- @
--     average = foldLeft $ (/) <$> sumF <*> lengthF
-- @

lambda-fairy

-- | <http://ncss.edu.au/challenge/ncss_challenge_2012.pdf>

class Semigroup a where
    (<>) :: a -> a -> a

data Result = Team String | Draw Int

resultLength :: Result -> Int
resultLength (Team name) = length name
resultLength (Draw lgth) = lgth