Crate winnow

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winnow, making parsing a breeze

winnow is a parser combinator library

Quick links:


winnow aims to be your “do everything” parser, much like people treat regular expressions.

In roughly priority order:

  1. Support writing parser declaratively while not getting in the way of imperative-style parsing when needed, working as an open-ended toolbox rather than a close-ended framework.
  2. Flexible enough to be used for any application, including parsing binary data, strings, or separate lexing and parsing phases
  3. Zero-cost abstractions, making it easy to write high performance parsers
  4. Easy to use, making it trivial for one-off uses

In addition:

  • Resilient maintainership, including
    • Willing to break compatibility rather than batching up breaking changes in large releases
    • Leverage feature flags to keep one active branch
  • We will support the last 6 months of rust releases (MSRV, currently 1.64.0)

See also [Special Topic: Why winnow?][crate::_topic::why]



$ cargo add winnow

Then use it to parse:

use winnow::prelude::*;
use winnow::token::take_while;

#[derive(Debug, Eq, PartialEq)]
pub struct Color {
    pub red: u8,
    pub green: u8,
    pub blue: u8,

impl std::str::FromStr for Color {
    // The error must be owned
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        hex_color.parse(s).map_err(|e| e.to_string())

pub fn hex_color(input: &mut &str) -> PResult<Color> {
    let _ = "#".parse_next(input)?;
    let (red, green, blue) = (hex_primary, hex_primary, hex_primary).parse_next(input)?;

    Ok(Color { red, green, blue })

fn hex_primary(input: &mut &str) -> PResult<u8> {
    take_while(2, |c: char| c.is_ascii_hexdigit())
        .try_map(|input| u8::from_str_radix(input, 16))

See also the [Tutorial][_tutorial::chapter_0] and [Special Topics][_topic]



  • Character specific parsers and combinators
  • Parsers recognizing numbers
  • List of parsers and combinators
  • Error management
  • Core concepts available for glob import
  • Stream capability for combinators to parse
  • Parsers extracting tokens from the stream
  • Parser execution tracing