Add inc, dec, ++, and --

fraction.cpp

@@ -109,6 +109,14 @@ namespace FractionNS {
     return *this / n;
   }
 
+  // Equivalent to ++x and --x, respectively
+  Fraction& Fraction::inc() {
+    return ++(*this);
+  }
+  Fraction& Fraction::dec() {
+    return --(*this);
+  }
+
   bool Fraction::operator==(const int n) const {
     return m_denominator == 1
         && m_numerator == n;
@@ -346,4 +354,26 @@ namespace FractionNS {
   Fraction& Fraction::operator+() const {
     return *new Fraction(m_numerator, m_denominator);
   }
+
+  // Prefix --
+  Fraction& Fraction::operator--() {
+    return *new Fraction(*this -= 1);
+  }
+  // Postfix --
+  Fraction& Fraction::operator--(const int) {
+    auto result = new Fraction(*this);
+    *this -= 1;
+    return *result;
+  }
+
+  // Prefix ++
+  Fraction& Fraction::operator++() {
+    return *new Fraction(*this += 1);
+  }
+  // Postfix ++
+  Fraction& Fraction::operator++(const int) {
+    auto result = new Fraction(*this);
+    *this += 1;
+    return *result;
+  }
 }

fraction.hpp

@@ -72,6 +72,8 @@ namespace FractionNS {
     Fraction& mul(const int) const;
     Fraction& div(const Fraction&) const;
     Fraction& div(const int) const;
+    Fraction& inc();
+    Fraction& dec();
 
     // Binary math operators
     Fraction& operator+(const int) const;
@@ -109,12 +111,10 @@ namespace FractionNS {
     Fraction& operator-() const;
     Fraction& operator+() const; // Should return a copy of the Fraction.
 
-    /*
     Fraction& operator++(); // ++x
     Fraction& operator++(const int); // x++
 
     Fraction& operator--(); // --x
     Fraction& operator--(const int); // x--
-    */
   };
 }

tst_fractiontest.cpp

@@ -31,6 +31,8 @@ private slots:
   void test_inverse();
   void test_pow();
   void test_math_methods();
+  void test_increment();
+  void test_decrement();
 };
 
 FractionTest::FractionTest() {
@@ -500,6 +502,30 @@ void FractionTest::test_math_methods() {
   QCOMPARE(f1 / f2, f1.div(f2));
 }
 
+void FractionTest::test_increment() {
+  Fraction f1 = Fraction(2);
+  const Fraction f2 = f1 + 1;
+  const Fraction f3 = f2 + 1;
+  const Fraction f4 = f3 + 1;
+
+  QCOMPARE(++f1, f2);
+  QCOMPARE(f1++, f2);
+  QCOMPARE(f1, f3);
+  QCOMPARE(f1.inc(), f4);
+}
+
+void FractionTest::test_decrement() {
+  Fraction f1 = Fraction(2);
+  const Fraction f2 = f1 - 1;
+  const Fraction f3 = f2 - 1;
+  const Fraction f4 = f3 - 1;
+
+  QCOMPARE(--f1, f2);
+  QCOMPARE(f1--, f2);
+  QCOMPARE(f1, f3);
+  QCOMPARE(f1.dec(), f4);
+}
+
 QTEST_APPLESS_MAIN(FractionTest)
 
 #include "tst_fractiontest.moc"