## Megaparsec 4.4.0
* Now state returned on failure is the exact state of parser at the moment
when it failed, which makes incremental parsing feature much better and
opens possibilities for features like “on-the-fly” recovering from parse
errors.
* The `count` combinator now works with `Applicative` instances (previously
it worked only with instances of `Alternative`). It's now also faster.
* `tokens` and parsers built upon it (such as `string` and `string'`)
backtrack automatically on failure now, that is, when they fail, they
never consume any input. This is done to make their consumption model
match how error messages are reported (which becomes an important thing as
user gets more control with primitives like `withRecovery`). This means,
in particular, that it's no longer necessary to use `try` with
`tokens`-based parsers. This new feature *does not* affect performance in
any way.
* New primitive parser `withRecovery` added. The parser allows to recover
from parse errors “on-the-fly” and continue parsing. Once parsing is
finished, several parse errors may be reported or ignored altogether.
* `eitherP` combinator added.
* Removed `Enum` instance of `Message` type. This was Parsec's legacy that
we should eliminate now. `Message` does not constitute enumeration,
`toEnum` was never properly defined for it. The idea to use `fromEnum` to
determine type of `Message` is also ugly, for this purpose new functions
`isUnexpected`, `isExpected`, and `isMessage` are defined in
`Text.Megaparsec.Error`.
* Minor tweak in signature of `MonadParsec` type class. Collection of
constraints changed from `Alternative m, Monad m, Stream s t` to
`Alternative m, MonadPlus m, Stream s t`. This is done to make it easier
to write more abstract code with older GHC where such primitives as
`guard` are defined for instances of `MonadPlus`, not `Alternative`.
## Megaparsec 4.3.0
* Canonicalized `Applicative`/`Monad` instances. Thanks to Herbert Valerio
Riedel.
* Custom messages in `ParseError` are printed each on its own line.
* Now accumulated hints are not used with `ParseError` records that have
only custom messages in them (created with `Message` constructor, as
opposed to `Unexpected` or `Expected`). This strips “expected” line from
custom error messages where it's unlikely to be relevant anyway.
* Added higher-level combinators for indentation-sensitive grammars:
`indentLevel`, `nonIndented`, and `indentBlock`.
## Megaparsec 4.2.0
* Made `newPos` constructor and other functions in `Text.Megaparsec.Pos`
smarter. Now it's impossible to create `SourcePos` with non-positive line
number or column number. Unfortunately we cannot use `Numeric.Natural`
because we need to support older versions of `base`.
* `ParseError` is now a monoid. `mergeError` is used as `mappend`.
* Added functions `addErrorMessages` and `newErrorMessages` to add several
messages to existing error and to construct error with several attached
messages respectively.
* `parseFromFile` now lives in `Text.Megaparsec.Prim`. Previously we had 5
nearly identical definitions of the function, varying only in
type-specific `readFile` function. Now the problem is solved by
introduction of `StorableStream` type class. All supported stream types
are instances of the class out of box and thus we have polymorphic version
of `parseFromFile`.
* `ParseError` is now instance of `Exception` (and `Typeable`).
* Introduced `runParser'` and `runParserT'` functions that take and return
parser state. This makes it possible to partially parse input, resume
parsing, specify non-standard initial textual position, etc.
* Introduced `failure` function that allows to fail with arbitrary
collection of messages. `unexpected` is now defined in terms of
`failure`. One consequence of this design decision is that `failure` is
now method of `MonadParsec`, while `unexpected` is not.
* Removed deprecated combinators from `Text.Megaparsec.Combinator`:
* `chainl`
* `chainl1`
* `chainr`
* `chainr1`
* `number` parser in `Text.Megaparsec.Lexer` now can be used with `signed`
combinator to parse either signed `Integer` or signed `Double`.
## Megaparsec 4.1.1
* Fixed bug in implementation of `sepEndBy` and `sepEndBy1` and removed
deprecation notes for these functions.
* Added tests for `sepEndBy` and `sepEndBy1`.
## Megaparsec 4.1.0
* Relaxed dependency on `base`, so that minimal required version of `base`
is now 4.6.0.0. This allows Megaparsec to compile with GHC 7.6.x.
* `Text.Megaparsec` and `Text.Megaparsec.Prim` do not export data types
`Consumed` and `Reply` anymore because they are rather low-level
implementation details that should not be visible to end-user.
* Representation of file name and textual position in error messages was
made conventional.
* Fixed some typos is documentation and other materials.
## 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 strings 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.