#macro #monad #do

mdo

Monadic do notation for rust using macro and duck typing

2 unstable releases

Uses old Rust 2015

0.3.0 Jun 23, 2016
0.2.0 Feb 10, 2015

#581 in Rust patterns

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121 downloads per month
Used in 2 crates

WTFPL license

10KB
214 lines

Rust mdo Build Status

Presentation

Rust mdo is a monadic do notation using macro and duck typing. It provides a syntax extention providing something looking like the Haskell do notation, and rewrite it using a bind function. Some functions are privided for some common monadic structures.

Example

Add to your Cargo.toml:

[dependencies]
mdo = "*"
#[macro_use] extern crate mdo;

fn main() {
    // exporting the monadic functions for the Iterator monad (similar
    // to list comprehension)
    use mdo::iter::{bind, ret, mzero};

    // getting the list of (x, y, z) such that
    //  - 1 <= x <= y < z < 11
    //  - x^2 + y^2 == z^2
    let l = bind(1i32..11, move |z|
                 bind(1..z, move |x|
                      bind(x..z, move |y|
                           bind(if x * x + y * y == z * z { ret(()) }
                                else { mzero() },
                                move |_|
                                ret((x, y, z))
                                )))).collect::<Vec<_>>();
    println!("{:?}", l);

    // the same thing, using the mdo! macro
    let l = mdo! {
        z =<< 1i32..11;
        x =<< 1..z;
        y =<< x..z;
        when x * x + y * y == z * z;
        ret ret((x, y, z))
    }.collect::<Vec<_>>();
    println!("{:?}", l);
}

Documentation

You can find the rustdoc here.

License

This work is free. You can redistribute it and/or modify it under the terms of the Do What The Fuck You Want To Public License, Version 2, as published by Sam Hocevar. See the COPYING file for more details.

No runtime deps