From e0f2378c221b1899e4f1c6668c3a21e6d8a73f8d Mon Sep 17 00:00:00 2001
From: Tobias Glaubach <tobias.glaubach@asinco.de>
Date: Tue, 17 Jul 2018 20:50:09 +0200
Subject: [PATCH] changed somne comments. improved the Trim implementation
 added a UnitTest for Trim

---
 src/Numerics.Tests/PolynomialTests.cs | 13 ++++++++++++
 src/Numerics/Polynomial.cs            | 29 +++++++++++----------------
 2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/src/Numerics.Tests/PolynomialTests.cs b/src/Numerics.Tests/PolynomialTests.cs
index b4b78eba..342cf67a 100644
--- a/src/Numerics.Tests/PolynomialTests.cs
+++ b/src/Numerics.Tests/PolynomialTests.cs
@@ -210,6 +210,19 @@ namespace MathNet.Numerics.UnitTests
         }
 
 
+        [TestCase(new double[] { 5, 4, 0 }, "5 + 4x^1")]
+        [TestCase(new double[] { 0, 0, 0 }, "0")]
+        [TestCase(new double[] { 5, 4, 3, 0, 2 }, "5 + 4x^1 + 3x^2 + 0x^3 + 2x^4")]
+        [TestCase(new double[] { 0, 0, 8, 0, 0 }, "0 + 0x^1 + 8x^2")]
+        [TestCase(new double[] { 0, 4, 3, 0, 0 }, "0 + 4x^1 + 3x^2")]
+        public void TrimTest(double[] x, string expected)
+        {
+            var p = new Polynomial(x);
+            p.Trim();
+            Assert.AreEqual(expected, p.ToString());
+
+        }
+
         public void DivideLongTestScalar(Tuple<double[], double> inVals, Tuple<double[], double> expectedVals)
         {
             var p1 = new Polynomial(1.0d);
diff --git a/src/Numerics/Polynomial.cs b/src/Numerics/Polynomial.cs
index 3213a5b3..4992f1d0 100644
--- a/src/Numerics/Polynomial.cs
+++ b/src/Numerics/Polynomial.cs
@@ -93,8 +93,8 @@ namespace MathNet.Numerics
         /// var xP1 = new Polynomial(x, isFlip:true);
         /// var xP2 = new Polynomial(x, isFlip:false);
         /// 
-        /// xP1:  5 x^3 + 4 x^2 + 3 x^2 + 0 x^1 + 2
-        /// xP2:  2 x^3 + 0 x^2 + 3 x^2 + 4 x^1 + 5
+        /// xP1:  2 + 0x^1 + 3x^2 + 4x^3 + 5x^4
+        /// xP2:  5 + 4x^1 + 3x^2 + 0x^3 + 2x^4
         /// 
         /// </summary>
         /// <param name="coeffs"> Polynomial coefficiens as array</param>
@@ -120,22 +120,17 @@ namespace MathNet.Numerics
         /// </summary>
         public void Trim()
         {
-            int count = 0;
-            for (int ii = Degree - 1; ii >= 0; ii--)
+            int i = Degree - 1;
+            while (i >= 0 && Coeffs[i] == 0.0)
+                i--;
+            
+            if (i < 0)
+                Coeffs = new double[0];
+            else
             {
-                if (Coeffs[ii] == 0.0)
-                {
-                    count++;
-                }
-                else
-                {
-                    double[] CoeffsHold = new double[Coeffs.Length];
-                    Coeffs.CopyTo(CoeffsHold, 0);
-                    Array.Resize(ref CoeffsHold, Degree - count);
-                    Coeffs = new double[Degree - count];
-                    CoeffsHold.CopyTo(Coeffs, 0);
-                    return;
-                }
+                var hold = new double[i+1];
+                Array.Copy(Coeffs, hold, i+1);
+                Coeffs = hold;
             }
         }