polyparse-1.1: A variety of alternative parser combinator libraries.ContentsIndex
Text.ParserCombinators.PolyStateLazy
Contents
The Parser datatype.
Combinators:
Primitives
Error-handling
Choices
Sequences
State-handling
Re-parsing
Synopsis
newtype Parser s t a = P (s -> [t] -> (Either String a, s, [t]))
runParser :: Parser s t a -> s -> [t] -> (a, s, [t])
failBad :: String -> Parser s t a
commit :: Parser s t a -> Parser s t a
next :: Parser s t t
satisfy :: (t -> Bool) -> Parser s t t
apply :: Parser s t (a -> b) -> Parser s t a -> Parser s t b
discard :: Parser s t a -> Parser s t b -> Parser s t a
adjustErr :: Parser s t a -> (String -> String) -> Parser s t a
adjustErrBad :: Parser s t a -> (String -> String) -> Parser s t a
indent :: Int -> String -> String
onFail :: Parser s t a -> Parser s t a -> Parser s t a
oneOf :: [Parser s t a] -> Parser s t a
oneOf' :: [(String, Parser s t a)] -> Parser s t a
optional :: Parser s t a -> Parser s t (Maybe a)
exactly :: Int -> Parser s t a -> Parser s t [a]
many :: Parser s t a -> Parser s t [a]
many1 :: Parser s t a -> Parser s t [a]
sepBy :: Parser s t a -> Parser s t sep -> Parser s t [a]
sepBy1 :: Parser s t a -> Parser s t sep -> Parser s t [a]
bracketSep :: Parser s t bra -> Parser s t sep -> Parser s t ket -> Parser s t a -> Parser s t [a]
bracket :: Parser s t bra -> Parser s t ket -> Parser s t a -> Parser s t a
manyFinally :: Parser s t a -> Parser s t z -> Parser s t [a]
stUpdate :: (s -> s) -> Parser s t ()
stQuery :: (s -> a) -> Parser s t a
stGet :: Parser s t s
reparse :: [t] -> Parser s t ()
The Parser datatype.
Parsers do not return explicit failure. An exception is raised instead. This allows partial results to be returned before a full parse is complete.
newtype Parser s t a
The Parser datatype is a fairly generic parsing monad with error reporting and a running state. It can be used for arbitrary token types, not just String input.
Constructors
P (s -> [t] -> (Either String a, s, [t]))
show/hide Instances
Monad (Parser s t)
Functor (Parser s t)
runParser :: Parser s t a -> s -> [t] -> (a, s, [t])
Apply a parser to an initial state and input token sequence. The parser cannot return an error value explicitly, so errors raise an exception. Thus, results can be partial (lazily constructed, but containing undefined).
failBad :: String -> Parser s t a
Simple failure can be corrected, but when a simple fail is not strong enough, use failBad for emphasis. It guarantees parsing will terminate with an exception.
commit :: Parser s t a -> Parser s t a
Commit is a way of raising the severity of any errors found within its argument. Used in the middle of a parser definition, it means that any operations prior to commitment fail softly, but after commitment, they fail hard.
Combinators:
Primitives
next :: Parser s t t
One token
satisfy :: (t -> Bool) -> Parser s t t
One token satifying a predicate
apply :: Parser s t (a -> b) -> Parser s t a -> Parser s t b
Apply a parsed function to a parsed value
discard :: Parser s t a -> Parser s t b -> Parser s t a
x discard y parses both x and y, but discards the result of y
Error-handling
adjustErr :: Parser s t a -> (String -> String) -> Parser s t a
p adjustErr f applies the transformation f to any error message generated in p, having no effect if p succeeds.
adjustErrBad :: Parser s t a -> (String -> String) -> Parser s t a
adjustErrBad is just like adjustErr except it also raises the severity of the error.
indent :: Int -> String -> String
Helper for formatting error messages: indents all lines by a fixed amount.
Choices
onFail :: Parser s t a -> Parser s t a -> Parser s t a
p onFail q means parse p unless p fails in which case parse q instead. Can be chained together to give multiple attempts to parse something. (Note that q could itself be a failing parser, e.g. to change the error message from that defined in p to something different.) However, a *severe* failure in p cannot be ignored.
oneOf :: [Parser s t a] -> Parser s t a
Parse the first alternative in the list that succeeds.
oneOf' :: [(String, Parser s t a)] -> Parser s t a
Parse the first alternative that succeeds, but if none succeed, report only the severe errors, and if none of those, then report all the soft errors.
optional :: Parser s t a -> Parser s t (Maybe a)
optional indicates whether the parser succeeded through the Maybe type.
Sequences
exactly :: Int -> Parser s t a -> Parser s t [a]
'exactly n p' parses a precise number of items, n, using the parser p, in sequence.
many :: Parser s t a -> Parser s t [a]
'many p' parses a list of elements with individual parser p. Cannot fail, since an empty list is a valid return value.
many1 :: Parser s t a -> Parser s t [a]
Parse a non-empty list of items.
sepBy :: Parser s t a -> Parser s t sep -> Parser s t [a]
Parse a list of items separated by discarded junk.
sepBy1 :: Parser s t a -> Parser s t sep -> Parser s t [a]
Parse a non-empty list of items separated by discarded junk.
bracketSep :: Parser s t bra -> Parser s t sep -> Parser s t ket -> Parser s t a -> Parser s t [a]
Parse a list of items, discarding the start, end, and separator items.
bracket :: Parser s t bra -> Parser s t ket -> Parser s t a -> Parser s t a
Parse a bracketed item, discarding the brackets.
manyFinally :: Parser s t a -> Parser s t z -> Parser s t [a]
'manyFinally e t' parses a possibly-empty sequence of e's, terminated by a t. Any parse failures could be due either to a badly-formed terminator or a badly-formed element, so raise both possible errors.
State-handling
stUpdate :: (s -> s) -> Parser s t ()
Update the internal state.
stQuery :: (s -> a) -> Parser s t a
Query the internal state.
stGet :: Parser s t s
Deliver the entire internal state.
Re-parsing
reparse :: [t] -> Parser s t ()
Push some tokens back onto the front of the input stream and reparse. This is useful e.g. 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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