Fixes #3: XYZPolynomial.add() changes values of its parameters

Author: porst17

src/main/java/de/mfo/jsurf/algebra/XYZPolynomial.java

@@ -147,6 +147,22 @@ public String longToString()
             result.append( "x^" + xExp + "y^" + yExp + "z^" + zExp );
             return result.toString();
         }
+
+        public boolean equals( Term t )
+        {
+            return this.coeff == t.coeff &&
+                this.xExp == t.xExp &&
+                this.yExp == t.yExp &&
+                this.zExp == t.zExp;
+        }
+
+        public int hashCode()
+        {
+            return ( ( int ) ( Double.doubleToRawLongBits( this.coeff ) % 0x00000000FFFFFFFFL ) ) &
+                ( ( int ) this.xExp ) &
+                ( ( int ) this.xExp ) << 8 &
+                ( ( int ) this.xExp ) << 16;
+        }
     }
 
     private Term[] terms; // ordered list of terms, such that terms[ i ].lexCompare( terms[ i + 1 ] ) < 0
@@ -158,6 +174,8 @@ public String longToString()
     private byte degree;
     private int numXyTerms; // number of terms in result of evaluateZ
     private boolean isCompact = false;
+    
+    private static final Term[] dummyTermArray = new Term[ 0 ];
 
     public XYZPolynomial()
     {
@@ -270,7 +288,7 @@ else if( lexCompare > 0 )
         while( i2 < terms2.length )
             resultTerms.add( new Term( terms2 [ i2++ ] ) );
 
-        return new XYZPolynomial( resultTerms.toArray( this.terms ) );
+        return new XYZPolynomial( resultTerms.toArray( XYZPolynomial.dummyTermArray ) );
     }
 
     public XYZPolynomial mult( XYZPolynomial p )
@@ -300,7 +318,7 @@ private static XYZPolynomial mult( XYZPolynomial p1, XYZPolynomial p2 )
             for( int i = 0; i < p2.terms.length; i++ )
                 resultTerms.add( t1.mult( p2.terms[ i ] ) );
         }
-        return new XYZPolynomial( collect( resultTerms.toArray( new Term[ 0 ] ), true ) );
+        return new XYZPolynomial( collect( resultTerms.toArray( XYZPolynomial.dummyTermArray ), true ) );
     }
 
 //    // standard polynomial multiplication (faster, but less numerically stable)
@@ -693,7 +711,7 @@ public XYZPolynomial substitute( XYZPolynomial xPoly, XYZPolynomial yPoly, XYZPo
             for( Term e : expandedTerm.terms )
                 terms.add( e );
         }
-        XYZPolynomial result = new XYZPolynomial( collect( terms.toArray( new Term[ 0 ] ), true ) );
+        XYZPolynomial result = new XYZPolynomial( collect( terms.toArray( XYZPolynomial.dummyTermArray ), true ) );
         return result;
     }
 */
@@ -724,7 +742,7 @@ private static Term[] collect( Term[] terms, boolean sort )
 
             if( resultTerms.size() == 0 )
                 resultTerms.add( new Term( 0.0, (byte) 0, (byte) 0, (byte) 0 ) );
-            return resultTerms.toArray( new Term[ 0 ] );
+            return resultTerms.toArray( XYZPolynomial.dummyTermArray );
         }
         else
         {
@@ -776,4 +794,22 @@ public double[][][] recursiveView()
             a[ t.zExp ][ t.yExp ][ t.xExp ] = t.coeff;
         return a;
     }
+
+    public boolean equals( XYZPolynomial p )
+    {
+        if( this.terms.length != p.terms.length )
+            return false;
+        for( int i = 0; i < this.terms.length; ++i )
+            if( !this.terms[ i ].equals( p.terms[ i ] ) )
+                return false;
+        return true;
+    }
+
+    public int hashCode()
+    {
+        int c = 0;
+        for( int i = 0; i < this.terms.length; ++i )
+            c += this.terms[ i ].hashCode();
+        return c;
+    }
 }

src/test/java/de/mfo/jsurf/test/TestJSurf.java

@@ -4,6 +4,7 @@
 
 import de.mfo.jsurf.rendering.cpu.CPUAlgebraicSurfaceRenderer;
 import de.mfo.jsurf.rendering.RenderingInterruptedException;
+import de.mfo.jsurf.algebra.*;
 import de.mfo.jsurf.util.FileFormat;
 import java.util.Properties;
 import javax.swing.SwingWorker;
@@ -54,4 +55,12 @@ public Void doInBackground() {
 
 		Assert.assertTrue( "stopDrawing must interrupt and stop the rendering process", t < 200 );
 	}
-}
+
+	@Test
+	public void XYZPolynomialAddShouldNotAffectMethodParameters()
+	{
+		XYZPolynomial X = new XYZPolynomial( XYZPolynomial.X );
+		XYZPolynomial.X.add( XYZPolynomial.X );
+		Assert.assertTrue( "XYZPolynomial.add changes values of its parameters", X.equals( XYZPolynomial.X ) );
+	}
+}