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Tim Pierson o1lo01ol1o

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@sheaf
sheaf / TAP.hs
Last active November 25, 2020 16:01
Using type applications in patterns to obtain the set of patterns tried in a pattern match at the type level
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedWildCards #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE PartialTypeSignatures #-}
@xgrommx
xgrommx / HRecursionSchemes.hs
Last active December 9, 2021 07:30
HRecursionSchemes
{-# LANGUAGE StandaloneDeriving, DataKinds, PolyKinds, GADTs, RankNTypes, TypeOperators, FlexibleContexts, TypeFamilies, KindSignatures #-}
-- http://www.timphilipwilliams.com/posts/2013-01-16-fixing-gadts.html
module HRecursionSchemes where
import Control.Applicative
import Data.Functor.Identity
import Data.Functor.Const
import Text.PrettyPrint.Leijen hiding ((<>))
@zmactep
zmactep / encodings.md
Created August 20, 2017 13:08
Number encodings

Alternative to the Church, Scott and Parigot encodings of data on the Lambda Calculus.

When it comes to encoding data on the pure λ-calculus (without complex extensions such as ADTs), there are 3 widely used approaches.

Church Encoding

The Church Encoding, which represents data structures as their folds. Using Caramel’s syntax, the natural number 3 is, for example. represented as:

0 c0 = (f x -> x)
1 c1 = (f x -> (f x))
2 c2 = (f x -&gt; (f (f x)))