parsec3-1.0.0.2: Monadic parser combinators

Portability portable provisional derek.a.elkins@gmail.com

Text.Parsec.Combinator

Description

Commonly used generic combinators

Synopsis

# Documentation

choice :: Stream s m t => [ParsecT s u m a] -> ParsecT s u m aSource

`choice ps` tries to apply the parsers in the list `ps` in order, until one of them succeeds. Returns the value of the succeeding parser.

count :: Stream s m t => Int -> ParsecT s u m a -> ParsecT s u m [a]Source

`count n p` parses `n` occurrences of `p`. If `n` is smaller or equal to zero, the parser equals to `return []`. Returns a list of `n` values returned by `p`.

between :: Stream s m t => ParsecT s u m open -> ParsecT s u m close -> ParsecT s u m a -> ParsecT s u m aSource

`between open close p` parses `open`, followed by `p` and `close`. Returns the value returned by `p`.

```  braces  = between (symbol "{") (symbol "}")
```

option :: Stream s m t => a -> ParsecT s u m a -> ParsecT s u m aSource

`option x p` tries to apply parser `p`. If `p` fails without consuming input, it returns the value `x`, otherwise the value returned by `p`.

```  priority  = option 0 (do{ d <- digit
; return (digitToInt d)
})
```

optionMaybe :: Stream s m t => ParsecT s u m a -> ParsecT s u m (Maybe a)Source

`optionMaybe p` tries to apply parser `p`. If `p` fails without consuming input, it return `Nothing`, otherwise it returns `Just` the value returned by `p`.

optional :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()Source

`optional p` tries to apply parser `p`. It will parse `p` or nothing. It only fails if `p` fails after consuming input. It discards the result of `p`.

skipMany1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m ()Source

`skipMany1 p` applies the parser `p` one or more times, skipping its result.

many1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m [a]Source

`many1 p` applies the parser `p` one or more times. Returns a list of the returned values of `p`.

```  word  = many1 letter
```

sepBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`sepBy p sep` parses zero or more occurrences of `p`, separated by `sep`. Returns a list of values returned by `p`.

```  commaSep p  = p `sepBy` (symbol ",")
```

sepBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`sepBy1 p sep` parses one or more occurrences of `p`, separated by `sep`. Returns a list of values returned by `p`.

endBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`endBy p sep` parses zero or more occurrences of `p`, seperated and ended by `sep`. Returns a list of values returned by `p`.

```   cStatements  = cStatement `endBy` semi
```

endBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`endBy1 p sep` parses one or more occurrences of `p`, seperated and ended by `sep`. Returns a list of values returned by `p`.

sepEndBy :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`sepEndBy p sep` parses zero or more occurrences of `p`, separated and optionally ended by `sep`, ie. haskell style statements. Returns a list of values returned by `p`.

```  haskellStatements  = haskellStatement `sepEndBy` semi
```

sepEndBy1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m sep -> ParsecT s u m [a]Source

`sepEndBy1 p sep` parses one or more occurrences of `p`, separated and optionally ended by `sep`. Returns a list of values returned by `p`.

chainl :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u m aSource

`chainl p op x` parser zero or more occurrences of `p`, separated by `op`. Returns a value obtained by a left associative application of all functions returned by `op` to the values returned by `p`. If there are zero occurrences of `p`, the value `x` is returned.

chainl1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u m aSource

`chainl1 p op x` parser one or more occurrences of `p`, separated by `op` Returns a value obtained by a left associative application of all functions returned by `op` to the values returned by `p`. . This parser can for example be used to eliminate left recursion which typically occurs in expression grammars.

```  expr    = term   `chainl1` addop
term    = factor `chainl1` mulop
factor  = parens expr <|> integer

mulop   =   do{ symbol "*"; return (*)   }
<|> do{ symbol "/"; return (div) }

addop   =   do{ symbol "+"; return (+) }
<|> do{ symbol "-"; return (-) }
```

chainr :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> a -> ParsecT s u m aSource

`chainr p op x` parser zero or more occurrences of `p`, separated by `op` Returns a value obtained by a right associative application of all functions returned by `op` to the values returned by `p`. If there are no occurrences of `p`, the value `x` is returned.

chainr1 :: Stream s m t => ParsecT s u m a -> ParsecT s u m (a -> a -> a) -> ParsecT s u m aSource

`chainr1 p op x` parser one or more occurrences of |p|, separated by `op` Returns a value obtained by a right associative application of all functions returned by `op` to the values returned by `p`.

eof :: (Stream s m t, Show t) => ParsecT s u m ()Source

This parser only succeeds at the end of the input. This is not a primitive parser but it is defined using `notFollowedBy`.

```  eof  = notFollowedBy anyToken <?> "end of input"
```

notFollowedBy :: (Stream s m t, Show a) => ParsecT s u m a -> ParsecT s u m ()Source

`notFollowedBy p` only succeeds when parser `p` fails. This parser does not consume any input. This parser can be used to implement the 'longest match' rule. For example, when recognizing keywords (for example `let`), we want to make sure that a keyword is not followed by a legal identifier character, in which case the keyword is actually an identifier (for example `lets`). We can program this behaviour as follows:

```  keywordLet  = try (do{ string "let"
; notFollowedBy alphaNum
})
```

manyTill :: Stream s m t => ParsecT s u m a -> ParsecT s u m end -> ParsecT s u m [a]Source

`manyTill p end` applies parser `p` zero or more times until parser `end` succeeds. Returns the list of values returned by `p`. This parser can be used to scan comments:

```  simpleComment   = do{ string "<!--"
; manyTill anyChar (try (string "-->"))
}
```

Note the overlapping parsers `anyChar` and `string "-->"`, and therefore the use of the `try` combinator.

lookAhead :: Stream s m t => ParsecT s u m a -> ParsecT s u m aSource

`lookAhead p` parses `p` without consuming any input.

anyToken :: (Stream s m t, Show t) => ParsecT s u m tSource

The parser `anyToken` accepts any kind of token. It is for example used to implement `eof`. Returns the accepted token.