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polyvariadic: Creation and application of polyvariadic functions

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Creation and application of polyvariadic functions, see the docs for usage and examples

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Versions 0.3.0.0, 0.3.0.1, 0.3.0.2, 0.3.0.3, 0.3.0.3, 0.3.0.4
Change log ChangeLog.md
Dependencies base (>=4.7 && <4.11), containers (>=0.1 && <0.6), semigroups (>=0.18 && <0.19) [details]
License BSD-3-Clause
Copyright (C) Francesco Gazzetta 2017
Author Francesco Gazzetta
Maintainer francygazz@gmail.com
Category Data
Home page https://github.com/fgaz/polyvariadic
Source repo head: git clone git://github.com/fgaz/polyvariadic.git
Uploaded by fgaz at 2017-12-19T17:37:40Z

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Readme for polyvariadic-0.3.0.3

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polyvariadic

Creation and application of polyvariadic functions

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For example, the classic printf:

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FlexibleContexts #-}
import Data.Function.Polyvariadic
import Data.Accumulator

magicChar = '%'
notMagicChar = (/= magicChar)

data PrintfAccum = PrintfAccum { done :: String, todo :: String }

instance Show x => Accumulator PrintfAccum x where
  accumulate x (PrintfAccum done (_:todo)) = PrintfAccum
                                              (done ++ show x ++ takeWhile notMagicChar todo)
                                              (dropWhile notMagicChar todo)
  accumulate _ acc = acc

printf' str = polyvariadic
               (PrintfAccum (takeWhile notMagicChar str) (dropWhile notMagicChar str))
               done

>>> printf' "aaa%bbb%ccc%ddd" "TEST" 123 True
"aaa\"TEST\"bbb123cccTrueddd"