add AlmostEqualsToZero() and AlmostEquals().

src/UglyToad.PdfPig.DocumentLayoutAnalysis/MathExtensions.cs

@@ -15,7 +15,7 @@
         /// <returns>The mode of the sequence. Returns <see cref="float.NaN"/> if the sequence has no mode or if it is not unique.</returns>
         public static float Mode(this IEnumerable<float> array)
         {
-            if (array == null || array.Count() == 0) return float.NaN;
+            if (array == null || !array.Any()) return float.NaN;
             var sorted = array.GroupBy(v => v).Select(v => (v.Count(), v.Key)).OrderByDescending(g => g.Item1);
             var mode = sorted.First();
             if (sorted.Count() > 1 && mode.Item1 == sorted.ElementAt(1).Item1) return float.NaN;
@@ -29,11 +29,32 @@
         /// <returns>The mode of the sequence. Returns <see cref="double.NaN"/> if the sequence has no mode or if it is not unique.</returns>
         public static double Mode(this IEnumerable<double> array)
         {
-            if (array == null || array.Count() == 0) return double.NaN;
+            if (array == null || !array.Any()) return double.NaN;
             var sorted = array.GroupBy(v => v).Select(v => (v.Count(), v.Key)).OrderByDescending(g => g.Item1);
             var mode = sorted.First();
             if (sorted.Count() > 1 && mode.Item1 == sorted.ElementAt(1).Item1) return double.NaN;
             return mode.Key;
         }
+
+        /// <summary>
+        /// Test for almost equality to 0.
+        /// </summary>
+        /// <param name="number"></param>
+        /// <param name="epsilon"></param>
+        public static bool AlmostEqualsToZero(this double number, double epsilon = 1e-5)
+        {
+            return (number > -epsilon) && (number < epsilon);
+        }
+
+        /// <summary>
+        /// Test for almost equality.
+        /// </summary>
+        /// <param name="number"></param>
+        /// <param name="other"></param>
+        /// <param name="epsilon"></param>
+        public static bool AlmostEquals(this double number, double other, double epsilon = 1e-5)
+        {
+            return AlmostEqualsToZero(number - other, epsilon);
+        }
     }
 }