Text.Parsing.StringParser

type Pos = Int

A position in an input string.

type PosString = { pos :: Pos, str :: String }

Strings are represented as a string with an index from the start of the string.

{ str: s, pos: n } is interpreted as the substring of s starting at index n.

This allows us to avoid repeatedly finding substrings every time we match a character.

type ParseError = { error :: String, pos :: Pos }

The type of parsing errors.

newtype Parser a

A parser is represented as a function that, when successful, returns a result and the position where the parse finished or, when it fails, a ParserError with more information on where and why it failed. See also printParserError.

Constructors

• Parser (PosString -> Either ParseError { result :: a, suffix :: PosString })

Instances

• Functor Parser
• Apply Parser
• Applicative Parser
• Alt Parser
• Plus Parser
• Alternative Parser
• Bind Parser
• Monad Parser
• MonadZero Parser
• MonadPlus Parser
• MonadRec Parser
• Lazy (Parser a)
• (Semigroup a) => Semigroup (Parser a)
• (Monoid a) => Monoid (Parser a)

unParser :: forall a. Parser a -> PosString -> Either ParseError { result :: a, suffix :: PosString }

Run a parser, allowing the caller to define where to start within the input String and what to do with the unchanged output of the Parser. See runparser for more typical usages.

runParser :: forall a. Parser a -> String -> Either ParseError a

Run a parser for an input string. See also printParserError and unParser for more flexible usages.

printParserError :: ParseError -> String

Prints a ParseError's the error message and the position of the error.

fail :: forall a. String -> Parser a

Fail with the specified message.

try :: forall a. Parser a -> Parser a

In case of error, the default behavior is to backtrack if no input was consumed.

try p backtracks even if input was consumed.