Execute a function once

JavaScript version

const once = (fn) =>
    (
        (ran = false) =>
        () =>
            ran ? fn : ((ran = !ran), (fn = fn()))
    )();

Examples

let n = 0;
const incOnce = once(() => ++n);
incOnce(); // n = 1
incOnce(); // n = 1
incOnce(); // n = 1