(function(){
	var vec2 = function (a,b){
		this.a = a
		this.b = b
	}
	vec2.prototype.magnitude = function(){
		return this.b-this.a
	}
	vec2.prototype.length = function(){
		return abs(this.b-this.a)
	}
	vec2.prototype.dist = function(){
		return dist(0,this.a,0,this.b)
	}
	vec2.prototype.clone = function(){
		return new vec2(this.a, this.b)
	}
	vec2.prototype.abs = function(){
		if (this.b < this.a) {
			this.invert()
		}
		return this
	}
	vec2.prototype.invert = function(){
		this.a = this.a ^ this.b
		this.b = this.a ^ this.b
		this.a = this.a ^ this.b
		return this
	}
	vec2.prototype.midpoint = function(){
		return lerp(0.5, this.a, this.b)
	}
	vec2.prototype.eq = function(v){
		return this.a == v.a && this.b == v.b
	}
	vec2.prototype.add = function(n){
		this.a += n
		this.b += n
		return this
	}
	vec2.prototype.sub = function(n){
		this.a -= n
		this.b -= n
		return this
	}
	vec2.prototype.mul = function(n){
		this.a *= n
		this.b *= n
		return this
	}
	vec2.prototype.div = function(n){
		this.a /= n
		this.b /= n
		return this
	}
	vec2.prototype.setPosition = function(n){
		var len = this.length()
		this.a = n
		this.b = n + len
	}
	vec2.prototype.setLength = function(n){
		this.b = this.a + n
	}
	vec2.prototype.normalize = function(){
		var dim = max(this.a, this.b)
		this.a = this.a/dim
		this.b = this.b/dim
		return this
	}
	vec2.prototype.contains = function(n){
		return this.a <= n && n <= this.b
	}
	vec2.prototype.containsCenter = function(n){
		return this.a < n && n < this.b
	}
	vec2.prototype.containsDisc = function(n,r){
		return this.a <= n-r && n+r <= this.b
	}
	vec2.prototype.clamp = function(n){
		return clamp(n, this.a, this.b)
	}
	vec2.prototype.clampDisc = function(n,r){
		return clamp(n, this.a+r, this.b-r)
	}
	vec2.prototype.intersects = function(v){
		if (this.a == v.a || this.b == v.b || this.a == v.b || this.b == v.a) {
			return true
		}
		else if (this.a < v.a) {
			return (v.a < this.b && this.b <= v.b) || (this.a < v.b && v.b <= this.b)
		}
		else if (this.a > v.a) {
			return (this.a < v.b && v.b <= this.b) || (v.a < this.b && this.b <= v.b)
		}
	}
	vec2.prototype.adjacent = function(v){
		if (this.a == v.a || this.b == v.b || this.a == v.b || this.b == v.a) {
			return true
		}
		return false
	}
	vec2.prototype.union = function(v){
		if (this.intersects(v)) {
			return new vec2( min(this.a,v.a), max(this.b, v.b) )
		}
	}
	vec2.prototype.intersection = function(v){
		if (this.intersects(v)) {
			return new vec2( max(this.a,v.a), min(this.b, v.b) )
		}
	}

	// given two vectors, test how they overlap
	// return the set of overlapping segments in the initial vector, labelled with sides
	vec2.prototype.split = function(v, left, right){
		var intervals = [], _len

		if (this.eq(v)) {
			intervals.push([ new vec2( this.a, this.b ), left | right ])
		}
		
		// a---A===b---B  (rightways overlap)
		else if (this.contains(v.a) && v.contains(this.b)) {
			intervals.push([ new vec2( this.a,    v.a ), left  ])
			intervals.push([ new vec2(    v.a, this.b ), right ])
		}

    // A---a===B---b  (leftways overlap)
		else if (v.contains(this.a) && this.contains(v.b)) {
			intervals.push([ new vec2( this.a,    v.b ), left  ])
			intervals.push([ new vec2(    v.b, this.b ), right ])
		}
	
		// a---A===B---b  (contains v)
		else if (this.contains(v.a) && this.contains(v.b)) {
			intervals.push([ new vec2( this.a,    v.a ), left  ])
			intervals.push([ new vec2(    v.a, 	  v.b ), 0     ])
			intervals.push([ new vec2(    v.b, this.b ), right ])
		}
		
		// A---a===b---B  (contained in v)
		else { // if (v.contains(this.a) && v.contains(v.b)) {
			intervals.push([ new vec2( this.a, this.b ), left | right ])
		}
		
		// cull empty vectors
		_len = intervals.length
		if (_len > 1) {
			if (intervals[0][0].magnitude() == 0) {
				intervals[1][1] |= intervals[0][1]
				intervals.shift()
			}
			else if (intervals[_len-1][0].magnitude() == 0) {
				intervals[_len-2][1] |= intervals[_len-1][1]
				intervals.pop()
			}
		}
		
		return intervals
	}

	vec2.prototype.toString = function(){
		return "[" + ~~this.a + " " + ~~this.b + "]"
	}
	vec2.prototype.serialize = function(){
		return [ ~~this.a, ~~this.b ]
	}
	vec2.prototype.quantize = function(n){
		n = n || 10
		this.a = quantize(this.a, n)
		this.b = quantize(this.b, n)
	}
	
	if ('window' in this) {
		window.vec2 = vec2
	}
	else {
		module.exports = vec2
	}
})()