Crate placeholder_closure

Scala’s Placeholder Syntax for Rust.

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.

let f = λ!($ + 1);

will be:

let f = |__0| __0 + 1;

Constructing move closures

You can also construct move closures.

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($)) })
}

Macros

lambda	An alias for λ!.
λ	Scala’s Placeholder Syntax for Rust.