_.util.trampolines.js.md

util.trampolines

Trampoline functions.

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done

Signature: _.done(value:Any)

A utility for wrapping a function's return values so they can be used by _.trampoline. See below.

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trampoline

Signature: _.trampoline(fun:Function[, args:Any...])

Provides a way of creating recursive functions that won't exceed a JavaScript engine's maximum recursion depth. Rather than writing a naive recursive function, the function's base cases must return _.done(someValue), and recursive calls must be wrapped in a returned function.

In order to create a trampolined function that can be used in the same way as a naive recursive function, use _.partial as illustrated below.

function isEvenNaive (num) {
    if (num === 0) return true;
    if (num === 1) return false;
    return isEvenNaive(num - 2);
}

isEvenNaive(99999);
// => InternalError: too much recursion

function isEvenInner (num) {
    if (num === 0) return _.done(true);
    if (num === 1) return _.done(false);
    return function () { return isEvenInner(Math.abs(num) - 2); };
}

_.trampoline(isEvenInner, 99999);
// => false

var isEven = _.partial(_.trampoline, isEvenInner);

isEven(99999);
// => false

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