Probably the hackiest enumerator i've built, Javascript.

enumerable.js

// Without the use of yield or enumerable definitions javascript makes enumerating over objects
// very difficult and verbose.

// Goes in Rectangle.js of my Geometry.js class
    this.trace = function(f) {
        if(this.width() > 1 && this.height() > 1) {
            // top
            (Rectangle.row(
                this.topLeft(), this.width() - 1
            )).enumerate(f);

            // right
            (Rectangle.column(
                (this.topRight()).offset(-1), this.height() - 1
            )).enumerate(f);

            // bottom
            (Rectangle.row(
                this.width() - 1
            )).enumerate(f, function(v) { 
                return ((this.bottomRight()).offset(-1, -1))['-'](v);
            });

            // left
            (Rectangle.column(
                this.height() - 1
            )).enumerate(f, function (v) {
                return ((this.bottomLeft()).offset(0, -1))['-'](v);
            });
        } else if(this.width() > 1 && this.height() == 1) {
            (Rectangle.row(
                this.topLeft(), this.width()
            )).enumerate(f);
        } else if(this.height() >= 1 && this.width() == 1) {
            (Rectangle.column(
                this.topLeft(), this.height()
            )).enumerate(f);
        }
    };

    this.enumerate = function (f, wrapper) {
        if(this.x() < 0 || this.y() < 0)
            return;

        for(var y = this.pos.y; y < (this.pos.y + this.size.y); y++) {
            for(var x = this.pos.x; x < (this.pos.x + this.size.x); x++) {
                if(wrapper) wrapper(f(new Vec2d(x, y)));
                else f(new Vec2d(x, y));
            }
        }
    };

good job!