regex_vs_markdown.md

Attoparsec Cheatsheet (vs. Regex)

Preconditions

• OverloadedString extension is applied.
• The following modules are imported.
  • Control.Applicative
  • Data.Attoparsec.Text
  • Data.Char

Cheatsheet

Regex	Attoparsec	Type
.	anyChar	Parser Char
x	char 'x'	Parser Char
foo	string "foo"	Parser Text
x*	many' (char 'x')	Parser [Char]
x*	takeWhile (== 'x')	Parser Text
x*	skipMany (char 'x')	Parser ()
x+	many1 (char 'x')	Parser [Char]
x+	takeWhile1 (== 'x')	Parser Text
x+	skipMany1 (char 'x')	Parser ()
x?	`fmap Just (char 'x') <	> pure Nothing`
[^x]	notChar 'x'	Parser Char
[^x]*	takeWhile (/= 'x')	Parser Text
[x-z]	satisfy (inClass "x-z")	Parser Char
[^x-z]	satisfy (notInClss "x-z")	Parser Char
[x-z]*	takeWhile (inClass "x-z")	Parser Text
(foo|bar)	string "foo" <|> string "bar"	Parser Text
(foo|bar)	choice (map string ["foo", "bar"])	Parser Text
(foo|bar)	eitherP (string "foo") (string "bar")	Parser (Either Text Text)
(foo){3}	count 3 (string "foo")	Parser [Text]
foo(,foo)*	string "foo" `seqBy` char ','	Parser [Text]
\s	space	Parser Char
\s	skipSpace	Parser ()
\S	satisfy (not . isSpace)	Parser Char
\w	satisfy (inClass "_a-zA-Z0-9")	Parser Char
\W	satisfy (notInClass "_a-zA-Z0-9")	Parser Char
\d	digit	Parser Char
\D	satisfy (not . isDigit)	Parser Char
\d+	decimal	Integral a => Parser a
	double	Parser Double
[0-9a-fA-F]	hexadecimal	(Integral a, Bits a) => Parser a

Example

{-# LANGUAGE OverloadedStrings #-}

import Data.Attoparsec.Text
import Prelude hiding (takeWhile)

parseCsvLine = parseOnly (takeWhile (/= ',') `sepBy` char ',')

main = print $ parseCsvLine "aaa,bbb,ccc"

$ runghc attoparsecexample.hs
Right ["aaa","bbb","ccc"]
$