implemented reduce() and __nonzero__()

frac.py

@@ -8,10 +8,13 @@ import numbers
 
 class frac:
     
-    def __init__(self, num, den):
+    def __init__(self, num, den, reduced = False):
+        if den == 0:
+            raise ValueError('frac denominator cannot be 0')
         self.num = long(num)
         self.den = long(den)
-        self.reduce()
+        if not reduced:
+            self.reduce()
     
     def __repr__(self):
         return 'frac(%d, %d)' % (self.num, self.den)
@@ -31,6 +34,12 @@ class frac:
     def __bool__(self):
         return bool(self.num)
     
+    def __nonzero__(self):
+        return self.__bool__()
+    
+    def __neg__(self):
+        return frac(-self.num, self.den, reduced=True)
+    
     def __add__(self, other):
         if isinstance(other, frac):
             newnum = self.num * other.den + other.num * self.den
@@ -133,4 +142,33 @@ class frac:
             return float(self) == other
     
     def reduce(self):
-        pass
+        pos = True
+        if self.num < 0:
+            pos = not pos
+            self.num = -self.num
+        if self.den < 0:
+            pos = not pos
+            self.den = -self.den
+        com = frac.gcd(self.num, self.den)
+        self.num /= com if pos else -com
+        self.den /= com
+    
+    #TODO: replace with more efficient version later
+    #https://en.wikipedia.org/wiki/Euclidean_algorithm
+    #if one number is 0 this returns the other number
+    #that works great for this application but may not for yours
+    @staticmethod
+    def gcd(num1, num2):
+        if num1 == 0:
+            return num2
+        elif num2 == 0:
+            return num1
+        elif num1 == num2:
+            return num1
+        elif num1 < num2:
+            temp = num1
+            num1 = num2
+            num2  = temp
+        return frac.gcd(num1 - num2, num2)
+    
+