@beenotung/tslib/maybe.js

utils library in Typescript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.Maybe = exports.Nothing = void 0;
const either_1 = require("./either");
const lang_1 = require("./lang");
exports.Nothing = {
    get() {
        throw new Error('Cannot get value from Nothing.');
    },
    isJust: false,
    isNothing: true,
    map: () => exports.Nothing,
    withDefault: a => Maybe.fromNullable(a),
    then: () => {
        return exports.Nothing;
    },
    otherwise: (f) => {
        f();
        return exports.Nothing;
    },
    toEither: (e) => (0, either_1.left)(e),
};
var Maybe;
(function (Maybe) {
    function fromNullable(a) {
        if ((0, lang_1.isDefined)(a)) {
            return {
                get: () => a,
                isJust: true,
                isNothing: false,
                map: (f) => fromNullable(f(a)),
                withDefault: _ => fromNullable(a),
                then: (f) => {
                    f(a);
                    return fromNullable(a);
                },
                otherwise: _ => fromNullable(a),
                toEither: (_e) => (0, either_1.right)(a),
            };
        }
        else {
            return exports.Nothing;
        }
    }
    Maybe.fromNullable = fromNullable;
    function or(a, b) {
        return a.isJust ? a : b.isJust ? b : exports.Nothing;
    }
    Maybe.or = or;
    function and(a, b) {
        return a.isJust && b.isJust
            ? fromNullable([a.get(), b.get()])
            : exports.Nothing;
    }
    Maybe.and = and;
})(Maybe || (exports.Maybe = Maybe = {}));