combine 1.0.0-beta.2

Parser combinators based on the Haskell library parsec. failed to build combine-1.0.0-beta.2
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(Previously parser-combinators)

An implementation of parser combinators for Rust, inspired by the Haskell library Parsec. As in Parsec the parsers are LL(1) by default but they can opt-in to arbitrary lookahed using the try combinator.

A parser combinators is, broadly speaking, a function which takes several parsers as arguments and returns a new parser, created by combining those parsers. For instance, the many parser takes one parser, p, as input and returns a new parser which applies p zero or more times.

The library is mostly stable but a few parts of the internals may still change. If you end up trying it I welcome any feedback from your experience with it.


extern crate combine;
use combine::{many, Parser};
use combine::char::letter;

let result = many(letter()).parse("hello world");
assert_eq!(result, Ok(("hello".to_string(), " world")));

More examples can be found in the examples and benches folders.


Documentation and examples


There is an additional crate which has parsers to lex and parse programming languages in combine-language.

Breaking changes

Here is a list containing most of the breaking changes in older versions of combine (parser-combinators).


  • Info<T> and Error<T> has had their signatures changed to Info<T, R> and Error<T, R>. Info has a new variant which is specified by R and defines the type for range errors. ParseError<T: Positioner> has been changed to ParseError<S: Stream> (S is the stream type of the parser).
  • If you were using ParseResult from primitives you should no longer specify the item type of the stream.


  • Stream::uncons changed its signature to allow it to return errors. Return Error::end_of_input() instead of () if you implemented Stream.


  • Addition of Parser::parse_lazy, should not break anything but I can't say for certain.


  • any_char -> any, uncons_char -> uncons
  • Introduction of the Positioner trait which needs to be implemented on an custom token types.
  • satisfy is moved to the combinators module and made generic, might cause type inference issues.


  • any_char is no longer a free function but returns a parser when called as all parser functions (and its called any after 0.5.0)
  • Cow is replaced by Info in the error messages.

0.3.2 / 0.3.0

  • Added variant to Error which can hold any kind of ::std::error::Error
  • choice_vec and choice_slice is replaced by just choice


  • Iterators cannot directly be used as streams but must be wrapped using from_iter function

If you have trouble updating to a newer version feel free to open an issue and I can take a look.