@edsilv/exjs/src/where.ts

Extension library

/// <reference path="enumerable.ts" />

namespace exjs {
    function whereEnumerator<T>(prev: IEnumerable<T>, filter: (t: T) => boolean): IEnumerator<T> {
        var t: IEnumerator<T>;
        var e = {
            current: undefined,
            moveNext: function (): boolean {
                if (!t) t = prev.getEnumerator();
                var c: T;
                while (t.moveNext()) {
                    if (filter(c = t.current)) {
                        e.current = c;
                        return true;
                    }
                }
                return false;
            }
        };
        return e;
    }

    Enumerable.prototype.where = function<T>(filter: (t: T) => boolean): IEnumerableEx<T> {
        var e = new Enumerable<T>();
        e.getEnumerator = () => whereEnumerator(<IEnumerable<T>>this, filter);
        return e;
    };
    if (List)
        List.prototype.where = Enumerable.prototype.where;
}