solves ticket #3531 and gives error for factorial of negative integersfactorial

1 files changed, 5 insertions, 10 deletions

diff --git a/functions.py b/functions.py
index 8a737ff..7bc5779 100644
--- a/functions.py
+++ b/functions.py
@@ -226,9 +226,9 @@ def exp(x):
     return math.exp(float(x))
 exp.__doc__ = _('exp(x), return the natural exponent of x. Given by e^x')
 
-def factorial(n):
-    if type(n) not in (types.IntType, types.LongType):
-        raise ValueError(_('Factorial only defined for integers'))
+def fac(n):
+    if type(n) not in (types.IntType, types.LongType) or n < 0:
+        raise ValueError(_('Factorial only defined for non-negative integers'))
 
     if n == 0:
         return 1
@@ -240,14 +240,9 @@ def factorial(n):
         n -= 1
 
     return res
-factorial.__doc__ = _(
-'factorial(n), return the factorial of n. \
-Given by n * (n - 1) * (n - 2) * ...')
-
-def fac(x):
-    return factorial(x)
 fac.__doc__ = _(
-'fac(x), return the factorial of x. Given by x * (x - 1) * (x - 2) * ...')
+'fac(n), returns the factorial of n. \
+Given by n * (n - 1) * (n - 2) * ...')
 
 def factorize(x):
     if not is_int(x):