polyparse Source code Contents Index

Text.ParserCombinators.HuttonMeijerWallace

Contents The parser monad Primitive parser combinators Derived combinators Error handling State handling Re-parsing

Description

This library of monadic parser combinators is based on the ones defined by Graham Hutton and Erik Meijer. It has been extended by Malcolm Wallace to use an abstract token type (no longer just a string) as input, and to incorporate state in the monad, useful for symbol tables, macros, and so on. Basic facilities for error reporting have also been added, and later extended by Graham Klyne to return the errors through an Either type, rather than just calling error.

Synopsis

newtype Parser s t e a = P (s -> [Either e t] -> ParseResult s t e a) item :: Parser s t e t eof :: Show p => Parser s (p, t) String () papply :: Parser s t String a -> s -> [Either String t] -> [(a, s, [Either String t])] papply' :: Parser s t e a -> s -> [Either e t] -> Either e [(a, s, [Either e t])] (+++) :: Parser s t e a -> Parser s t e a -> Parser s t e a tok :: Eq t => t -> Parser s (p, t) e t nottok :: Eq t => [t] -> Parser s (p, t) e t many :: Parser s t e a -> Parser s t e [a] many1 :: Parser s t e a -> Parser s t e [a] sepby :: Parser s t e a -> Parser s t e b -> Parser s t e [a] sepby1 :: Parser s t e a -> Parser s t e b -> Parser s t e [a] chainl :: Parser s t e a -> Parser s t e (a -> a -> a) -> a -> Parser s t e a chainl1 :: Parser s t e a -> Parser s t e (a -> a -> a) -> Parser s t e a chainr :: Parser s t e a -> Parser s t e (a -> a -> a) -> a -> Parser s t e a chainr1 :: Parser s t e a -> Parser s t e (a -> a -> a) -> Parser s t e a ops :: [(Parser s t e a, b)] -> Parser s t e b bracket :: (Show p, Show t) => Parser s (p, t) e a -> Parser s (p, t) e b -> Parser s (p, t) e c -> Parser s (p, t) e b toEOF :: Show p => Parser s (p, t) String a -> Parser s (p, t) String a elserror :: (Show p, Show t) => Parser s (p, t) String a -> String -> Parser s (p, t) String a stupd :: (s -> s) -> Parser s t e () stquery :: (s -> a) -> Parser s t e a stget :: Parser s t e s reparse :: [Either e t] -> Parser s t e ()

The parser monad

newtype Parser s t e a Source

Constructors P (s -> [Either e t] -> ParseResult s t e a) The parser type is parametrised on the types of the state s, the input tokens t, error-type e, and the result value a. The state and remaining input are threaded through the monad. Instances Monad (Parser s t e) Functor (Parser s t e) MonadPlus (Parser s t e)

Primitive parser combinators

item :: Parser s t e t Source

Deliver the first remaining token.

eof :: Show p => Parser s (p, t) String () Source

Fail if end of input is not reached

papply :: Parser s t String a -> s -> [Either String t] -> [(a, s, [Either String t])] Source

Apply the parser to some real input, given an initial state value. If the parser fails, raise error to halt the program. (This is the original exported behaviour - to allow the caller to deal with the error differently, see papply'.)

papply' :: Parser s t e a -> s -> [Either e t] -> Either e [(a, s, [Either e t])] Source

Apply the parser to some real input, given an initial state value. If the parser fails, return a diagnostic message to the caller.

Derived combinators

(+++) :: Parser s t e a -> Parser s t e a -> Parser s t e a Source

A choice between parsers. Keep only the first success.

tok :: Eq t => t -> Parser s (p, t) e t Source

Deliver the first token if it equals the argument.

nottok :: Eq t => [t] -> Parser s (p, t) e t Source

Deliver the first token if it does not equal the argument.

many :: Parser s t e a -> Parser s t e [a] Source

Deliver zero or more values of a.

many1 :: Parser s t e a -> Parser s t e [a] Source

Deliver one or more values of a.

sepby :: Parser s t e a -> Parser s t e b -> Parser s t e [a] Source

Deliver zero or more values of a separated by b's.

sepby1 :: Parser s t e a -> Parser s t e b -> Parser s t e [a] Source

Deliver one or more values of a separated by b's.

chainl :: Parser s t e a -> Parser s t e (a -> a -> a) -> a -> Parser s t e a Source

chainl1 :: Parser s t e a -> Parser s t e (a -> a -> a) -> Parser s t e a Source

chainr :: Parser s t e a -> Parser s t e (a -> a -> a) -> a -> Parser s t e a Source

chainr1 :: Parser s t e a -> Parser s t e (a -> a -> a) -> Parser s t e a Source

ops :: [(Parser s t e a, b)] -> Parser s t e b Source

bracket :: (Show p, Show t) => Parser s (p, t) e a -> Parser s (p, t) e b -> Parser s (p, t) e c -> Parser s (p, t) e b Source

toEOF :: Show p => Parser s (p, t) String a -> Parser s (p, t) String a Source

Accept a complete parse of the input only, no partial parses.

Error handling

elserror :: (Show p, Show t) => Parser s (p, t) String a -> String -> Parser s (p, t) String a Source

If the parser fails, generate an error message.

State handling

stupd :: (s -> s) -> Parser s t e () Source

Update the internal state.

stquery :: (s -> a) -> Parser s t e a Source

Query the internal state.

stget :: Parser s t e s Source

Deliver the entire internal state.

Re-parsing

reparse :: [Either e t] -> Parser s t e () Source

This is useful for recursively expanding macros. When the user-parser recognises a macro use, it can lookup the macro expansion from the parse state, lex it, and then stuff the lexed expansion back down into the parser.

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