comp-rs

Pure-macro Do notation and List-comprehension for Option, Result and Iterator.

It provides syntax extensions to easily combind wrapper type (Option, Result and Iterator), which seems like for-comprehension in scala or Do notation in haskell.

Documentation

Usage

First, add the following to your Cargo.toml:

toml [dependencies] comp = "0.1"

Next, add this to your crate root:

```rust

[macro_use]

extern crate comp; ```

Example

comp-rs delivers three macros : option!, result! and iter!, transforming the arrow(<-) statements into FP bind (flat_map).

Iterator

```rust

[macro_use]

extern crate comp;

let iter = iter! { let x <- 0..2u8; let y <- vec!['a', 'b']; (x, y) };

for x in iter { println!("{:?}", x); }

// Print (0, 'a') (0, 'b') (1, 'a') (1, 'b') ```

Option

```rust

[macro_use]

extern crate comp;

let option = option! { let a <- Some(1); let b <- Some(2); a + b };

assert_eq!(option, Some(3)); ```

Result

Unlike Iterator and Option, rust provides Question Mark syntax to combine Results.

Let's see how comp-rs makes it more explicit and expressive.

Native way

```rust

[macro_use]

extern crate comp;

use std::fs::File; use std::io; use std::io::prelude::*;

// try!() macro must be wrap into a function fn content() -> io::Result { let mut f = try!(File::open("foo.txt")); let mut s = String::new(); try!(f.readtostring(&mut s)); Ok(s) } ```

Question mark

```rust

[macro_use]

extern crate comp;

use std::fs::File; use std::io; use std::io::prelude::*;

// '?' mark must be wrap into a function fn content() -> io::Result { let mut f = File::open("foo.txt")?; let mut s = String::new(); f.readtostring(&mut s)?; Ok(s) } ```

result! way

```rust

[macro_use]

extern crate comp;

use std::fs::File; use std::io; use std::io::prelude::*;

let content: io::Result = result! { let mut f <- File::open("foo.txt"); let mut s = String::new(); let _ <- f.readtostring(&mut s); s }; ```

Contribution

All kinds of contribution are welcome.

• Issue Feel free to open an issue when you find typos, bugs, or have any question.
• Pull requests. Better implementation, more tests, more documents and typo fixes are all welcome.

License

Licensed under MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)