return {
	compare: compare,
	compose: compose,
	defined: defined,
	id: id,
	insert: insert,
	map: map,
	mapFilter: mapFilter,
	of: of,
	proj: proj
};

function compare(on) {
	on = on || id;
	return function(a, b) {
		var va = on(a), vb = on(b);
		return va < vb ? -1 : (va > vb ? 1 : 0)
	};
}

function compose(f, g) {
	return function() {
		return f(g.apply(null, arguments));
	};
}

function defined(x) {
	return x != undefined;
}

function id(x) {
	return x;
}

function insert(obj, t, comparer, min, max) {
	min = defined(min) ? min : 0;
	max = defined(max) ? max : t.length;
	comparer = comparer || compare();
	if(max - min < 1) {
		return min;
	}
	var avg = Math.floor((max + min) / 2);
	if (compare(obj, t[avg]) < 0) {
		return insert(obj, t, compare, min, avg);
	} else {
		return insert(obj, t, compare, avg+1, max);
	}
}

function map(mapper, f) {
	return function() {
		var args = Array.prototype.map.call(arguments, mapper);
		return f.apply(null, args);
	}
}

function mapFilter(mapper, predicate) {
	return function(array) {
		return array.reduce(function(accumulator, elem) {
			var v = mapper(elem);
			return predicate(v) ? accumulator.concat(v) : accumulator;
		}, []);
	};
}

function of(o) {
	return function(key) {return o[key];};
}

function proj(key) {
	return function(o) {return o[key];};
}