Various small enhancements

3 files changed, 79 insertions, 14 deletions

diff --git a/Week7/src/polynomial/Polynomial.java b/Week7/src/polynomial/Polynomial.java
index f7b1194..f7f9860 100644
--- a/Week7/src/polynomial/Polynomial.java
+++ b/Week7/src/polynomial/Polynomial.java
@@ -116,7 +116,7 @@ public class Polynomial {
                 return;
             }
         }
-        terms.add(t);
+        terms.add(new Term(t));
     }
 
     /**
@@ -124,8 +124,9 @@ public class Polynomial {
      * @param p the polynomial to subtract
      */
     public void minus(Polynomial p) {
-        p.times(new Polynomial("-1 0"));
-        plus(p);
+        Polynomial temp = new Polynomial(p);
+        temp.times(new Polynomial("-1 0"));
+        plus(temp);
     }
 
     /**
@@ -136,7 +137,7 @@ public class Polynomial {
         Polynomial result = new Polynomial();
         for (Term that_t : p.terms) 
             for (Term this_t : terms)
-                result.plus(new Polynomial((that_t.getCoef() * this_t.getCoef()) + " " + (that_t.getExp() + this_t.getExp())));
+                result.plus(new Term(that_t.getCoef() * this_t.getCoef(), that_t.getExp() + this_t.getExp()));
         terms = result.terms;
     }
 
@@ -153,7 +154,7 @@ public class Polynomial {
         if (other_poly == null || other_poly.getClass() != getClass())
             return false;
         
-        Polynomial that = (Polynomial) other_poly;
+        Polynomial that = new Polynomial((Polynomial) other_poly);      // We need to copy because later we'll remove elements
         if (terms.size() != that.terms.size()) 
             return false;
         for (Term this_t : terms) {
diff --git a/Week7/src/polynomial/Term.java b/Week7/src/polynomial/Term.java
index 7cde927..60c6381 100644
--- a/Week7/src/polynomial/Term.java
+++ b/Week7/src/polynomial/Term.java
@@ -81,17 +81,21 @@ public class Term {
     /**
      * Converts a term into a readable representation the standard format is
      * %fx^%d
+     * I changed the implementation to remove trailing zeroes from the coefficient.
      *
      * @return the string representing the term
      */
     @Override
     public String toString() {
+        String nice_coefficient = Double.toString(coefficient);
+        if (Math.round(coefficient) == coefficient)
+            nice_coefficient =  Integer.toString((int) coefficient);
         if (exponent == 0) {
-            return String.format("%f", coefficient, exponent);
+            return String.format("%s", nice_coefficient, exponent);
         } else if (exponent == 1) {
-            return String.format("%fx", coefficient, exponent);
+            return String.format("%sx", nice_coefficient, exponent);
         } else {
-            return String.format("%fx^%d", coefficient, exponent);
+            return String.format("%sx^%d", nice_coefficient, exponent);
         }
     }
 
diff --git a/Week7/test/polynomial/PolynomialTest.java b/Week7/test/polynomial/PolynomialTest.java
index c0f9c4b..8560dfb 100644
--- a/Week7/test/polynomial/PolynomialTest.java
+++ b/Week7/test/polynomial/PolynomialTest.java
@@ -1,8 +1,3 @@
-/*
- * To change this license header, choose License Headers in Project Properties.
- * To change this template file, choose Tools | Templates
- * and open the template in the editor.
- */
 package polynomial;
 
 import org.junit.After;
@@ -44,7 +39,7 @@ public class PolynomialTest {
     public void testToString() {
         System.out.println("toString");
         // Test exp=0, exp=1, exp>1, positive & negative integer & floating point coefficients all at once
-        assertEquals("3.000000x^5-4.000000x+2.500000-3.400000x^-7", new Polynomial("3 5 -4 1 2.5 0 -3.4 -7").toString());
+        assertEquals("3x^5-4x+2.5-3.4x^-7", new Polynomial("3 5 -4 1 2.5 0 -3.4 -7").toString());
         // Test zero polynomial
         assertEquals("", new Polynomial().toString());
     }
@@ -59,6 +54,33 @@ public class PolynomialTest {
         Polynomial instance = new Polynomial("7 4 -4 2 3 1 5 0");       // 7x^4 - 4x^2 + 3x + 5
         instance.minus(new Polynomial("5 3 4 2 3 1 10 0"));             // 5x^3 + 4x^2 + 3x + 10
         assertEquals(new Polynomial("7 4 -5 3 -8 2 -5 0"), instance);   // 7x^4 - 5x^3 - 8x^2 - 5
+        
+        // Test minus = plus (times -1) on many small 2-term polynomials
+        for (float c1 = -10; c1 < 10; c1 += 2.3)
+            for (int exp1 = 5; exp1 < 10; exp1++)
+                for (float c2 = -10; c2 < 10; c2 += 2.3)
+                    for (int exp2 = 5; exp2 < 10; exp2++) {
+                        Polynomial fst = new Polynomial(c1 + " " + exp1 + " " + c2 + " " + exp2);
+                        Polynomial snd = new Polynomial(c1 + " " + exp2 + " " + c2 + " " + exp1);
+                        Polynomial fst_2 = new Polynomial(fst);
+                        Polynomial snd_2 = new Polynomial(snd);
+                        fst.minus(snd);
+                        snd_2.times(new Polynomial("-1 0"));
+                        fst_2.plus(snd_2);
+                        assertEquals(true, fst.equals(fst_2));
+                    }
+        
+        // Test associativity for some random polynomials
+        Polynomial a = new Polynomial("5 4 2 5 20 8 4 0");
+        Polynomial b = new Polynomial("9 2 48 2 10 8 28 2");
+        Polynomial c = new Polynomial("3 8 4 20 8 2 4 5 0 0");
+        Polynomial a_bc = new Polynomial(a);
+        a_bc.minus(b);
+        a_bc.minus(c);
+        Polynomial a_cb = new Polynomial(a);
+        a_cb.minus(c);
+        a_cb.minus(b);
+        assertEquals(true, a_bc.equals(a_cb));
     }
 
     /**
@@ -82,6 +104,25 @@ public class PolynomialTest {
         instance = new Polynomial("4 4 2 3");                           // 4x^4 + 2x^3
         instance.times(new Polynomial("2 2 -4 3"));                     // 2x^2 - 4x^3
         assertEquals(new Polynomial("4 5 -16 7"), instance);            // 4x^5 - 16x^7 (exponent 6 cancels out)
+        
+        // Test associativity for some random polynomials
+        Polynomial a = new Polynomial("5 4 2 5 20 8 4 0");
+        Polynomial b = new Polynomial("9 2 48 2 10 8 28 2");
+        Polynomial c = new Polynomial("3 8 4 20 8 2 4 5 0 0");
+        Polynomial a_bc = new Polynomial(a);
+        a_bc.times(b);
+        a_bc.times(c);
+        Polynomial a_cb = new Polynomial(a);
+        a_cb.times(c);
+        a_cb.times(b);
+        assertEquals(true, a_bc.equals(a_cb));
+        
+        // Test commutativity
+        Polynomial a_b = new Polynomial(a);
+        a_b.times(b);
+        Polynomial b_a = new Polynomial(b);
+        b_a.times(a);
+        assertEquals(true, a_b.equals(b_a));
     }
 
     /**
@@ -127,6 +168,25 @@ public class PolynomialTest {
         Polynomial instance = new Polynomial("7 4 -4 2 7 1 5 0");       // 7x^4 - 4x^2 + 7x + 5
         instance.plus(new Polynomial("5 3 4 2 3 1 10 0"));              // 5x^3 + 4x^2 + 3x + 10
         assertEquals(new Polynomial("7 4 5 3 10 1 15 0"), instance);    // 7x^4 + 5x^3 + 10x + 15
+        
+        // Test associativity for some random polynomials
+        Polynomial a = new Polynomial("5 4 2 5 20 8 4 0");
+        Polynomial b = new Polynomial("9 2 7 5 10 8 28 2");
+        Polynomial c = new Polynomial("3 8 4 20 8 2 4 5 0 0");
+        Polynomial a_bc = new Polynomial(a);
+        a_bc.plus(b);
+        a_bc.plus(c);
+        Polynomial a_cb = new Polynomial(a);
+        a_cb.plus(c);
+        a_cb.plus(b);
+        assertEquals(true, a_bc.equals(a_cb));
+        
+        // Test commutativity
+        Polynomial a_b = new Polynomial(a);
+        a_b.plus(b);
+        Polynomial b_a = new Polynomial(b);
+        b_a.plus(a);
+        assertEquals(true, a_b.equals(b_a));
     }
 
     /**