placeholder_closure

Scala's Placeholder Syntax for Rust.

use placeholder_closure::λ;

let xs = xs.into_iter().map(λ!($ + 1)).collect::<Vec<_>>();

fn dot<F: FnOnce(Y) -> Z, G: FnOnce(X) -> Y, X, Y, Z>(f: F, g: G) -> impl FnOnce(X) -> Z {
    λ!(move { f(g($)) })
}

Usage

See the documentation on Docs.rs.

License

Licensed under CC0-1.0.

lib.rs:

Scala's Placeholder Syntax for Rust.

# let xs = vec![1, 2, 3, 4, 5];
use placeholder_closure::λ;

let xs = xs.into_iter().map(λ!($ + 1)).collect::<Vec<_>>();

How it works

The λ! (or lambda!) macro replaces 0 or more $ characters with closure arguments.

# use placeholder_closure::λ;
let f = λ!($ + 1);
# let _: fn(i32) -> i32 = f;

will be:

# use placeholder_closure::λ;
let f = |__0| __0 + 1;
# let _: fn(i32) -> i32 = f;

Constructing move closures

You can also construct move closures.

# use placeholder_closure::λ;
fn dot<F: FnOnce(Y) -> Z, G: FnOnce(X) -> Y, X, Y, Z>(f: F, g: G) -> impl FnOnce(X) -> Z {
    λ!(move { f(g($)) })
}