Like count, but packs its result

Like string, but uses Text.

Parse any line of text, returning the contents without the final newline.

Parse any line, include the final newline in the output

Parse indent by specified number of spaces (or equiv. tabs)

Like many, but packs its result.

Like many1, but packs its result.

Like manyTill, but packs its result.

Like many1Till, but packs its result

Like manyTill, but reads at least one item.

Like manyTill, but also returns the result of end parser.

Like manyUntil, but also packs its result.

Like sepBy1 from Parsec, but does not fail if it sep succeeds and p fails.

A more general form of notFollowedBy. This one allows any type of parser to be specified, and succeeds only if that parser fails. It does not consume any input.

Parses one of a list of strings. If the list contains two strings one of which is a prefix of the other, the longer string will be matched if possible.

Parses one of a list of strings (tried in order), case insensitive.

Parses a space or tab.

Parses a nonspace, nonnewline character.

Skips zero or more spaces or tabs.

Skips zero or more spaces or tabs, then reads a newline.

Parses one or more blank lines and returns a string of newlines.

Gobble n spaces; if tabs are encountered, expand them and gobble some or all of their spaces, leaving the rest.

Gobble up to n spaces; if tabs are encountered, expand them and gobble some or all of their spaces, leaving the rest.

Parses material enclosed between start and end parsers.

Parse string, case insensitive.

Parse contents of str using parser and return result.

Like parseFromString but specialized for ParserState. This resets stateLastStrPos, which is almost always what we want.

Parse raw line block up to and including blank lines.

Parse a string of characters between an open character and a close character, including text between balanced pairs of open and close, which must be different. For example, charsInBalanced '(' ')' anyChar will parse "(hello (there))" and return "hello (there)".

Parses a roman numeral (uppercase or lowercase), returns number.

Parses an email address; returns original and corresponding escaped mailto: URI.

Parses a URI. Returns pair of original and URI-escaped version.

Applies a parser, returns tuple of its results and its horizontal displacement (the difference between the source column at the end and the source column at the beginning). Vertical displacement (source row) is ignored.

Applies a parser and returns the raw string that was parsed, along with the value produced by the parser.

Parses backslash, then applies character parser.

Parse character entity.

Parses an uppercase roman numeral and returns (UpperRoman, number).

Parses a lowercase roman numeral and returns (LowerRoman, number).

Parses a decimal numeral and returns (Decimal, number).

Parses a lowercase letter and returns (LowerAlpha, number).

Parses an uppercase letter and returns (UpperAlpha, number).

Parses an ordered list marker and returns list attributes.

Parses an ordered list marker with a given style and delimiter, returns number.

Parses a character reference and returns a Str element.

Parses an RST-style line block and returns a list of strings.

Parse a table using headerParser, rowParser, lineParser, and footerParser.

Parse a string with a given parser and state

Removes the ParsecT layer from the monad transformer stack

Parse a string with parser (for testing).

Succeed only if the extension is enabled.

Succeed only if the extension is disabled.

Update the position on which the last string ended.

Whether we are right after the end of a string.

Add a log message.

Report all the accumulated log messages, according to verbosity level.

Parsing options.

Reader monad wrapping the parser state. This is used to possibly delay evaluation until all relevant information has been parsed and made available in the parser state.

An instance of Stream has stream type s, underlying monad m and token type t determined by the stream

Some rough guidelines for a "correct" instance of Stream:

• unfoldM uncons gives the [t] corresponding to the stream
• A Stream instance is responsible for maintaining the "position within the stream" in the stream state s. This is trivial unless you are using the monad in a non-trivial way.

The most general way to run a parser over the Identity monad. runParser p state filePath input runs parser p on the input list of tokens input, obtained from source filePath with the initial user state st. The filePath is only used in error messages and may be the empty string. Returns either a ParseError (Left) or a value of type a (Right).

 parseFromFile p fname
   = do{ input <- readFile fname
       ; return (runParser p () fname input)
       }

The most general way to run a parser. runParserT p state filePath input runs parser p on the input list of tokens input, obtained from source filePath with the initial user state st. The filePath is only used in error messages and may be the empty string. Returns a computation in the underlying monad m that return either a ParseError (Left) or a value of type a (Right).

parse p filePath input runs a parser p over Identity without user state. The filePath is only used in error messages and may be the empty string. Returns either a ParseError (Left) or a value of type a (Right).

 main    = case (parse numbers "" "11, 2, 43") of
            Left err  -> print err
            Right xs  -> print (sum xs)

 numbers = commaSep integer

The parser tokenPrim showTok nextPos testTok accepts a token t with result x when the function testTok t returns Just x. The token can be shown using showTok t. The position of the next token should be returned when nextPos is called with the current source position pos, the current token t and the rest of the tokens toks, nextPos pos t toks.

This is the most primitive combinator for accepting tokens. For example, the char parser could be implemented as:

 char c
   = tokenPrim showChar nextPos testChar
   where
     showChar x        = "'" ++ x ++ "'"
     testChar x        = if x == c then Just x else Nothing
     nextPos pos x xs  = updatePosChar pos x

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

Returns the current input

setInput input continues parsing with input. The getInput and setInput functions can for example be used to deal with #include files.

The parser unexpected msg always fails with an unexpected error message msg without consuming any input.

The parsers fail, (<?>) and unexpected are the three parsers used to generate error messages. Of these, only (<?>) is commonly used. For an example of the use of unexpected, see the definition of notFollowedBy.

skipMany p applies the parser p zero or more times, skipping its result.

 spaces  = skipMany space

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

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.

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"

lookAhead p parses p without consuming any input.

If p fails and consumes some input, so does lookAhead. Combine with try if this is undesirable.

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
                      })

NOTE: Currently, notFollowedBy exhibits surprising behaviour when applied to a parser p that doesn't consume any input; specifically

• notFollowedBy . notFollowedBy is not equivalent to lookAhead, and
• notFollowedBy eof never fails.

See haskell/parsec#8 for more details.

many p applies the parser p zero or more times. Returns a list of the returned values of p.

 identifier  = do{ c  <- letter
                 ; cs <- many (alphaNum <|> char '_')
                 ; return (c:cs)
                 }

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

 word  = many1 letter

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.

This combinator implements choice. The parser p <|> q first applies p. If it succeeds, the value of p is returned. If p fails without consuming any input, parser q is tried. This combinator is defined equal to the mplus member of the MonadPlus class and the (<|>) member of Alternative.

The parser is called predictive since q is only tried when parser p didn't consume any input (i.e.. the look ahead is 1). This non-backtracking behaviour allows for both an efficient implementation of the parser combinators and the generation of good error messages.

The parser p <?> msg behaves as parser p, but whenever the parser p fails without consuming any input, it replaces expect error messages with the expect error message msg.

This is normally used at the end of a set alternatives where we want to return an error message in terms of a higher level construct rather than returning all possible characters. For example, if the expr parser from the try example would fail, the error message is: '...: expecting expression'. Without the (<?>) combinator, the message would be like '...: expecting "let" or letter', which is less friendly.

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.

The parser try p behaves like parser p, except that it pretends that it hasn't consumed any input when an error occurs.

This combinator is used whenever arbitrary look ahead is needed. Since it pretends that it hasn't consumed any input when p fails, the (<|>) combinator will try its second alternative even when the first parser failed while consuming input.

The try combinator can for example be used to distinguish identifiers and reserved words. Both reserved words and identifiers are a sequence of letters. Whenever we expect a certain reserved word where we can also expect an identifier we have to use the try combinator. Suppose we write:

 expr        = letExpr <|> identifier <?> "expression"

 letExpr     = do{ string "let"; ... }
 identifier  = many1 letter

If the user writes "lexical", the parser fails with: unexpected 'x', expecting 't' in "let". Indeed, since the (<|>) combinator only tries alternatives when the first alternative hasn't consumed input, the identifier parser is never tried (because the prefix "le" of the string "let" parser is already consumed). The right behaviour can be obtained by adding the try combinator:

 expr        = letExpr <|> identifier <?> "expression"

 letExpr     = do{ try (string "let"); ... }
 identifier  = many1 letter

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

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

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

  cStatements  = cStatement `endBy` semi

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

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)
                         })

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.

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.

Returns the current user state.

An alias for putState for backwards compatibility.

An alias for modifyState for backwards compatibility.

The abstract data type SourcePos represents source positions. It contains the name of the source (i.e. file name), a line number and a column number. SourcePos is an instance of the Show, Eq and Ord class.

Returns the current source position. See also SourcePos.

setPosition pos sets the current source position to pos.

Extracts the name of the source from a source position.

Set the name of the source.

Extracts the column number from a source position.

Extracts the line number from a source position.

Set the column number of a source position.

Set the line number of a source position.

Increments the column number of a source position.

Increments the line number of a source position.

Create a new SourcePos with the given source name, line number and column number.

Create a new SourcePos with the given source name, and line number and column number set to 1, the upper left.

The abstract data type ParseError represents parse errors. It provides the source position (SourcePos) of the error and a list of error messages (Message). A ParseError can be returned by the function parse. ParseError is an instance of the Show and Eq classes.