close #397

src/Shared/HandyControl_Shared/Expression/Drawing/MathHelper.cs

@@ -4,6 +4,8 @@ namespace HandyControl.Expression.Drawing
 {
     internal static class MathHelper
     {
+        internal const double DBL_EPSILON = 2.2204460492503131e-016;
+
         public static bool AreClose(double value1, double value2) =>
             // ReSharper disable once CompareOfFloatsByEqualityOperator
             value1 == value2 || IsVerySmall(value1 - value2);
@@ -12,6 +14,8 @@ namespace HandyControl.Expression.Drawing
 
         public static bool IsVerySmall(double value) => Math.Abs(value) < 1E-06;
 
+        public static bool IsZero(double value) => Math.Abs(value) < 10.0 * DBL_EPSILON;
+
         public static bool IsFiniteDouble(double x) => !double.IsInfinity(x) && !double.IsNaN(x);
 
         public static double DoubleFromMantissaAndExponent(double x, int exp) => x * Math.Pow(2.0, exp);