megaparsec

Megaparsec 4.0.0

General changes

• Renamed many1 → some as well as other parsers that had many1 part in their names.

• The following functions are now re-exported from Control.Applicative: (<|>), many, some, optional. See #9.

• Introduced type class MonadParsec in the style of MTL monad transformers. Eliminated built-in user state since it was not flexible enough and can be emulated via stack of monads. Now all tools in Megaparsec work with any instance of MonadParsec, not only with ParsecT.

• Added new function parseMaybe for lightweight parsing where error messages (and thus file name) are not important and entire input should be parsed. For example it can be used when parsing of single number according to specification of its format is desired.

• Fixed bug with notFollowedBy always succeeded with parsers that don’t consume input, see #6.

• Flipped order of arguments in the primitive combinator label, see #21.

• Renamed tokenPrim → token, removed old token, because tokenPrim is more general and original token is little used.

• Made token parser more powerful, now its second argument can return Either [Message] a instead of Maybe a, so it can influence error message when parsing of token fails. See #29.

• Added new primitive combinator hidden p which hides “expected” tokens in error message when parser p fails.

• Tab width is not hard-coded anymore. It can be manipulated via getTabWidth and setTabWidth. Default tab-width is defaultTabWidth, which is 8.

Error messages

• Introduced type class ShowToken and improved representation of characters and stings in error messages, see #12.

• Greatly improved quality of error messages. Fixed entire Text.Megaparsec.Error module, see #14 for more information. Made possible normal analysis of error messages without “render and re-parse” approach that previous maintainers had to practice to write even simplest tests, see module Utils.hs in old-tests for example.

• Reduced number of Message constructors (now there are only Unexpected, Expected, and Message). Empty “magic” message strings are ignored now, all the library now uses explicit error messages.

• Introduced hint system that greatly improves quality of error messages and made code of Text.Megaparsec.Prim a lot clearer.

Built-in combinators

• All built-in combinators in Text.Megaparsec.Combinator now work with any instance of Alternative (some of them even with Applicaitve).

• Added more powerful count' parser. This parser can be told to parse from m to n occurrences of some thing. count is defined in terms of count'.

• Removed optionMaybe parser, because optional from Control.Applicative does the same thing.

• Added combinator someTill.

• These combinators are considered deprecated and will be removed in future:

  • chainl
  • chainl1
  • chainr
  • chainr1
  • sepEndBy
  • sepEndBy1

Character parsing

• Renamed some parsers:

  • alphaNum → alphaNumChar
  • digit → digitChar
  • endOfLine → eol
  • hexDigit → hexDigitChar
  • letter → letterChar
  • lower → lowerChar
  • octDigit → octDigitChar
  • space → spaceChar
  • spaces → space
  • upper → upperChar

• Added new character parsers in Text.Megaparsec.Char:

  • asciiChar
  • charCategory
  • controlChar
  • latin1Char
  • markChar
  • numberChar
  • printChar
  • punctuationChar
  • separatorChar
  • symbolChar

• Descriptions of old parsers have been updated to accent some Unicode-specific moments. For example, old description of letter stated that it parses letters from “a” to “z” and from “A” to “Z”. This is wrong, since it used Data.Char.isAlpha predicate internally and thus parsed many more characters (letters of non-Latin languages, for example).

• Added combinators char', oneOf', noneOf', and string' which are case-insensitive variants of char, oneOf, noneOf, and string respectively.

Lexer

• Rewritten parsing of numbers, fixed #2 and #3 (in old Parsec project these are number 35 and 39 respectively), added per bug tests.

  • Since Haskell report doesn’t say anything about sign, integer and float now parse numbers without sign.

  • Removed natural parser, it’s equal to new integer now.

  • Renamed naturalOrFloat → number — this doesn’t parse sign too.

  • Added new combinator signed to parse all sorts of signed numbers.

• Transformed Text.Parsec.Token into Text.Megaparsec.Lexer. Little of Parsec’s code remains in the new lexer module. New module doesn’t impose any assumptions on user and should be vastly more useful and general. Hairy stuff from original Parsec didn’t get here, for example built-in Haskell functions are used to parse escape sequences and the like instead of trying to re-implement the whole thing.

Other

• Renamed the following functions:

  • permute → makePermParser
  • buildExpressionParser → makeExprParser

• Added comprehensive QuickCheck test suite.

• Added benchmarks.

Parsec 3.1.9

• Many and various updates to documentation and package description (including the homepage links).

• Add an Eq instance for ParseError.

• Fixed a regression from 3.1.6: runP is again exported from module Text.Parsec.

Parsec 3.1.8

• Fix a regression from 3.1.6 related to exports from the main module.

Parsec 3.1.7

• Fix a regression from 3.1.6 related to the reported position of error messages. See bug #9 for details.

• Reset the current error position on success of lookAhead.

Parsec 3.1.6

• Export Text instances from Text.Parsec.

• Make Text.Parsec exports more visible.

• Re-arrange Text.Parsec exports.

• Add functions crlf and endOfLine to Text.Parsec.Char for handling input streams that do not have normalized line terminators.

• Fix off-by-one error in Token.charControl.

Parsec 3.1.4 & 3.1.5

• Bump dependency on text.

Parsec 3.1.3

• Fix a regression introduced in 3.1.2 related to positions reported by error messages.