parsec-3.1.7: Monadic parser combinators

Copyright | (c) Paolo Martini 2007
License | BSD-style (see the LICENSE file)
Maintainer | derek.a.elkins@gmail.com
Stability | provisional
Portability | portable
Safe Haskell | Safe-Inferred
Language | Haskell98

Text.ParserCombinators.Parsec.Error

Description

Parsec compatibility module

Synopsis

- data Message
  - = SysUnExpect !String
  - | UnExpect !String
  - | Expect !String
  - | Message !String
- messageString :: Message -> String
- messageCompare :: Message -> Message -> Ordering
- messageEq :: Message -> Message -> Bool
- data ParseError
- errorPos :: ParseError -> SourcePos
- errorMessages :: ParseError -> [Message]
- errorIsUnknown :: ParseError -> Bool
- showErrorMessages :: String -> String -> String -> String -> String -> [Message] -> String
- newErrorMessage :: Message -> SourcePos -> ParseError
- newErrorUnknown :: SourcePos -> ParseError
- addErrorMessage :: Message -> ParseError -> ParseError
- setErrorPos :: SourcePos -> ParseError -> ParseError
- setErrorMessage :: Message -> ParseError -> ParseError
- mergeError :: ParseError -> ParseError -> ParseError

# Documentation

data Message

This abstract data type represents parse error messages. There are four kinds of messages:

     data Message = SysUnExpect String
                  | UnExpect String
                  | Expect String
                  | Message String

The fine distinction between different kinds of parse errors allows the system to generate quite good error messages for the user. It also allows error messages that are formatted in different languages. Each kind of message is generated by different combinators:

- A `SysUnExpect` message is automatically generated by the `satisfy` combinator. The argument is the unexpected input.
  - A `UnExpect` message is generated by the `unexpected` combinator. The argument describes the unexpected item.
  - A `Expect` message is generated by the `<?>` combinator. The argument describes the expected item.
  - A `Message` message is generated by the `fail` combinator. The argument is some general parser message.

Constructors

SysUnExpect !String |
UnExpect !String |
Expect !String |
Message !String |

Instances

Enum Message |
Eq Message |
Ord Message |

messageString :: Message -> String

Extract the message string from an error message

messageCompare :: Message -> Message -> Ordering

messageEq :: Message -> Message -> Bool

data ParseError

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` class.

Instances

Show ParseError |

errorPos :: ParseError -> SourcePos

Extracts the source position from the parse error

errorMessages :: ParseError -> [Message]

Extracts the list of error messages from the parse error

errorIsUnknown :: ParseError -> Bool

showErrorMessages :: String -> String -> String -> String -> String -> [Message] -> String

newErrorMessage :: Message -> SourcePos -> ParseError

newErrorUnknown :: SourcePos -> ParseError

addErrorMessage :: Message -> ParseError -> ParseError

setErrorPos :: SourcePos -> ParseError -> ParseError

setErrorMessage :: Message -> ParseError -> ParseError

mergeError :: ParseError -> ParseError -> ParseError