@beenotung/tslib/functional/monad.js

utils library in Typescript

"use strict";
/**
 * monad factory
 * reference : https://github.com/douglascrockford/monad/blob/master/monad.js
 * */
Object.defineProperty(exports, "__esModule", { value: true });
exports.createUnit = createUnit;
const array_1 = require("../array");
function createUnit(modifier) {
    const prototype = Object.create(null);
    prototype.is_monad = true;
    const unit = Object.assign(function unit(value) {
        return unitFunction(value);
    });
    function unitFunction(value) {
        const bind = (f, args) => f.call(void 0, value, ...(0, array_1.toArray)(args || []));
        const map = (f, args) => bind((a, args) => unit(f.call(void 0, a, ...args)), args);
        const monad = {
            is_monad: true,
            bind,
            map,
        };
        if (typeof modifier === 'function') {
            value = modifier(monad, value);
        }
        return monad;
    }
    const method = (name, f) => {
        prototype[name] = f;
        return unit;
    };
    const lift_value = (name, f) => {
        prototype[name] = function () {
            const monad = this;
            return monad.bind(f, arguments);
        };
        return unit;
    };
    const lift = (name, f) => {
        prototype[name] = function () {
            const monad = this;
            return monad.bind((a, args) => {
                const b = f(a, ...args);
                if (b.is_monad) {
                    return b;
                }
                else {
                    return unit(b);
                }
            }, arguments);
        };
        return unit;
    };
    return Object.assign(unit, {
        method,
        lift_value,
        lift,
    });
}