peggy

The Parser Generator for Haskell http://tanakh.github.com/Peggy

Latest on Hackage:0.3.2

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow stackage.org to host generated Haddocks.

BSD3 licensed by Hideyuki Tanaka
Maintained by Hideyuki Tanaka

Peggy: A Parser Generator of Parsing Expression Grammer (PEG)

About

This is an yet another parser generator of Parsing Expression Grammer (PEG) which is:

  • Simple
  • Concise
  • Fast
  • Modern

Usage

You can find a recent stable release in Hackage DB. You can install this as following instruction:

$ cabal update
$ cabal install Peggy

Why should you use Peggy?

Haskell has commonly used parser generators, one of them are Alex/Happy. But I think Alex/Happy are not good in these points:

  • Generates regacy codes

Alex uses only too basic libraries. It does not use monad-transformers, iteratee, ListLike, Text, and so on.

  • Tradisional Regexp/CFG based parser

Parsec has no good error recovery.

unnun, kannun...

...

Quick Start

Here is an example of parsing arithmetic expressions.

{-# QuasiQuotes #-}
{-# Language FlexibleContexts #-}

import Text.Peggy

[peggy|
exp :: Double
  = exp "+" fact  { $1 + $2 }
  / exp "-" fact  { $1 - $2 }
  / fact
fact :: Double
  = fact "*" term { $1 * $2 }
  / fact "/" term { $1 / $2 }
  / term
term :: Double
  = "(" exp ")"
  / number
number ::: Double
  = ([1-9][0-9]*) { read $1 }
|]

main :: IO ()
main =
  print . parse exp =<< getContents
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