https://github.com/dandandan/parser

Parser combinator library for Elm
https://github.com/dandandan/parser

Last synced: 2 months ago
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Parser combinator library for Elm

• Host: GitHub
• URL: https://github.com/dandandan/parser
• Owner: Dandandan
• Created: 2014-06-19T14:20:27.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2016-11-29T10:03:20.000Z (about 8 years ago)
• Last Synced: 2024-06-19T01:58:09.302Z (7 months ago)
• Language: Elm
• Homepage:
• Size: 60.5 KB
• Stars: 36
• Watchers: 9
• Forks: 13
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md

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README

        
**Parser**

======

Parsers convert text sequences into a data structure, for example

for handling user input and compiling programming languages.

With this parser combinator you can build parsers in a modular way, building

parsers by combining parser functions. Parser functions can either succeed or

fail.

Examples

======

```elm

{-| Parse a optional sign, succeeds with a -1 if it matches a minus `Char`, otherwise it returns 1 -}

sign : Parser Int

sign =

    let

        minus =

            map (always -1) (symbol '-')

        plus =

            map (always 1) (symbol '+')

    in

        optional (or plus minus) 1

{-| Parse a digit -}

digit : Parser Int

digit =

    let

        charToInt c = Char.toCode c - Char.toCode '0'

    in

        map charToInt (satisfy Char.isDigit)

{-| Parse a natural number -}

natural : Parser Int

natural =

    some digit

    |> map (List.foldl (\b a -> a * 10 + b) 0)

{-| Parse an integer with optional sign -}

integer : Parser Int

integer =

    map (*) sign

    |> andMap natural

```