Module easy

Stream wrapper which provides an informative and easy to use error type.

Unless you have specific constraints preventing you from using this error type (such as being a no_std environment) you probably want to use this stream type. It can easily be used through the Parser::easy_parse method.

The provided Errors type is roughly the same as ParseError in combine 1.x and 2.x.

#[macro_use]
extern crate combine;
use combine::{easy, Parser, Stream, many1};
use combine::parser::char::letter;
use combine::stream::StreamErrorFor;
use combine::error::{ParseError, StreamError};

fn main() {
    parser!{
       fn parser[I]()(I) -> String
        where [
            I: Stream<Item=char, Error = easy::ParseError<I>>,
            // If we want to use the error type explicitly we need to help rustc infer
            // `StreamError` to `easy::Error` (rust-lang/rust#24159)
            I::Error: ParseError<
                I::Item,
                I::Range,
                I::Position,
                StreamError = easy::Error<I::Item, I::Range>
            >
        ]
        {
            many1(letter()).and_then(|word: String| {
                if word == "combine" {
                    Ok(word)
                } else {
                    Err(easy::Error::Expected(easy::Info::Borrowed("combine")))
                }
            })
        }
    }

    parser!{
       fn parser2[I]()(I) -> String
        where [
            I: Stream<Item=char>,
        ]
        {
            many1(letter()).and_then(|word: String| {
                if word == "combine" {
                    Ok(word)
                } else {
                    // Alternatively it is possible to only use the methods provided by the
                    // `StreamError` trait.
                    // In that case the extra bound is not necessary (and this method will work
                    // for other errors than `easy::Errors`)
                    Err(StreamErrorFor::<I>::expected_static_message("combine"))
                }
            })
        }
    }

    let input = "combin";
    let expected_error = Err(easy::Errors {
        errors: vec![
            easy::Error::Expected("combine".into())
        ],
        position: 0,
    });
    assert_eq!(
        parser().easy_parse(input).map_err(|err| err.map_position(|p| p.translate_position(input))),
        expected_error
    );
    assert_eq!(
        parser2().easy_parse(input).map_err(|err| err.map_position(|p| p.translate_position(input))),
        expected_error
    );
}

Structs

• Errors
  Struct which hold information about an error that occurred at a specific position. Can hold multiple instances of Error if more that one error occurred in the same position.
• Stream

Enums

• Error
  Enum used to store information about an error that has occurred during parsing.
• Info
  Enum holding error information. Variants are defined for Stream::Item and Stream::Range as well as string variants holding easy descriptions.

Type Aliases

• ParseError
  Convenience alias over Errors for StreamOnce types which makes it possible to specify the Errors type from a StreamOnce by writing ParseError<I> instead of Errors<I::Item, I::Range, I::Position>