Introduce Numerical.isZero(), for comparisons against 0 with a tolerance.

src/basic/Line.js

@@ -75,7 +75,7 @@ var Line = this.Line = Base.extend(/** @lends Line# */{
 	intersect: function(line) {
 		var cross = this.vector.cross(line.vector);
 		// Avoid divisions by 0, and errors when getting too close to 0
-		if (Math.abs(cross) <= Numerical.EPSILON)
+		if (Numerical.isZero(cross))
 			return null;
 		var v = line.point.subtract(this.point),
 			t1 = v.cross(line.vector) / cross,
@@ -96,7 +96,7 @@ var Line = this.Line = Base.extend(/** @lends Line# */{
 		var v1 = this.vector,
 			v2 = point.subtract(this.point),
 			ccw = v2.cross(v1);
-		if (ccw == 0) {
+		if (ccw === 0) {
 			ccw = v2.dot(v1);
 			if (ccw > 0) {
 				ccw = v2.subtract(v1).dot(v1);

src/basic/Matrix.js

@@ -446,7 +446,7 @@ var Matrix = this.Matrix = Base.extend(/** @lends Matrix# */{
 	 */
 	_getDeterminant: function() {
 		var det = this._a * this._d - this._b * this._c;
-		return isFinite(det) && Math.abs(det) > Numerical.EPSILON
+		return isFinite(det) && !Numerical.isZero(det)
 				&& isFinite(this._tx) && isFinite(this._ty)
 				? det : null;
 	},

src/basic/Point.js

@@ -701,7 +701,7 @@ var Point = this.Point = Base.extend(/** @lends Point# */{
 	 * @returns {Boolean} {@true both x and y are 0}
 	 */
 	isZero: function() {
-		return this.x == 0 && this.y == 0;
+		return Numerical.isZero(this.x) && Numerical.isZero(this.y);
 	},
 
 	/**

src/basic/Size.js

@@ -360,7 +360,7 @@ var Size = this.Size = Base.extend(/** @lends Size# */{
 	 * @return {Boolean} {@true both width and height are 0}
 	 */
 	isZero: function() {
-		return this.width == 0 && this.height == 0;
+		return Numerical.isZero(this.width) && Numerical.isZero(this.height);
 	},
 
 	/**

src/path/Curve.js

@@ -724,10 +724,7 @@ var Curve = this.Curve = Base.extend(/** @lends Curve# */{
 			// with x-axis.
 			if (isFlatEnough(w)) {
 				var line = new Line(w[0], w[5], true);
-				// Compare the line's squared length with EPSILON. If we're
+				return [ Numerical.isZero(line.vector.getLength(true))
-				// below, #intersect() will return null because of division
-				// by near-zero.
-				return [ line.vector.getLength(true) <= Numerical.EPSILON
 						? line.point.x
 						: xAxis.intersect(line).x ];
 			}

src/path/SegmentPoint.js

@@ -51,7 +51,7 @@ var SegmentPoint = Point.extend({
 		// Provide our own version of Point#isZero() that does not use the x / y
 		// accessors but the internal properties directly, for performance
 		// reasons, since it is used a lot internally.
-		return this._x == 0 && this._y == 0;
+		return Numerical.isZero(this._x) && Numerical.isZero(this._y);
 	},
 
 	setSelected: function(selected) {

src/util/Numerical.js

@@ -74,7 +74,15 @@ var Numerical = new function() {
 		EPSILON: 10e-12,
 
 		/**
-		 * Gauss-Legendre Numerical Integration
+		 * Check if the value is 0, within a tolerance defined by
+		 * Numerical.EPSILON.
+		 */
+		isZero: function(val) {
+			return Math.abs(val) <= this.EPSILON;
+		},
+
+		/**
+		 * Gauss-Legendre Numerical Integration.
 		 */
 		integrate: function(f, a, b, n) {
 			var x = abscissas[n - 2],