closure_list.js

function list(v) {
	function errchk(f, e) {
		try {
			return f();
		} catch (err) {
			if (err instanceof ReferenceError &&
				err.message.match(/^[v]+\s/) !== null) {
				return e ? e() : undefined;
			}
			
			throw err;
		}
	}
	
	var fn = {
		add: function (val) {
			return eval('(' + list.toString()
				.replace(/\(([v]+)\)/, '($1v)') + ')')(val);
		},
		get: function (i) {
			if (i < 0) {
				throw new RangeError();
			}
			
			return errchk(function () {
				return eval(Array(i + 2).join('v'));
			}, function () {
				throw new RangeError();
			});
		},
		set: function (i, val) {
			this.get(i);
			
			eval(Array(i + 2).join('v') + ' = val');
		},
		each: function (f) {
			errchk(function () {
				for (var vs = 'v';; vs += 'v') {
					f(eval(vs));
				}
			});
		},
		to_a: function () {
			var a = [];
			this.each(a.push.bind(a));
			return a;
		}
	};
	
	Object.keys(fn).forEach(function (k) {
		fn[k] = fn[k].bind(fn);
	});
	
	return fn;
}

// uso / usage:
var l1 = list('hola');
var l2 = l1.add('como').add('estas');
l1 = l1.add('javier');

l2.set(0, 'hello'); // === l1.set(0, 'hello')

console.log(l1.to_a().join(' '));
console.log(l2.to_a().join(' '));