September Morn Update

Task/Factorial/Python/factorial-4.py

@@ -1,5 +1,8 @@
+from itertools import (accumulate, chain)
+from operator import mul
+
+# factorial :: Integer
 def factorial(n):
-    z=1
-    if n>1:
-        z=n*factorial(n-1)
-    return z
+    return list(
+        accumulate(chain([1], range(1, 1 + n)), mul)
+    )[-1]

Task/Factorial/Python/factorial-5.py

@@ -1,27 +1,13 @@
-from cmath import *
+from itertools import (accumulate, chain)
+from operator import mul
 
-# Coefficients used by the GNU Scientific Library
-g = 7
-p = [0.99999999999980993, 676.5203681218851, -1259.1392167224028,
-     771.32342877765313, -176.61502916214059, 12.507343278686905,
-     -0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7]
 
-def gamma(z):
-  z = complex(z)
-  # Reflection formula
-  if z.real < 0.5:
-    return pi / (sin(pi*z)*gamma(1-z))
-  else:
-    z -= 1
-    x = p[0]
-    for i in range(1, g+2):
-      x += p[i]/(z+i)
-    t = z + g + 0.5
-    return sqrt(2*pi) * t**(z+0.5) * exp(-t) * x
+# factorials :: [Integer]
+def factorials(n):
+    return list(
+        accumulate(chain([1], range(1, 1 + n)), mul)
+    )
 
-def factorial(n):
-  return gamma(n+1)
+print(factorials(5))
 
-print "factorial(-0.5)**2=",factorial(-0.5)**2
-for i in range(10):
-  print "factorial(%d)=%s"%(i,factorial(i))
+# -> [1, 1, 2, 6, 24, 120]

Task/Factorial/Python/factorial-6.py

@@ -0,0 +1,5 @@
+def factorial(n):
+    z=1
+    if n>1:
+        z=n*factorial(n-1)
+    return z

Task/Factorial/Python/factorial-7.py

@@ -0,0 +1,27 @@
+from cmath import *
+
+# Coefficients used by the GNU Scientific Library
+g = 7
+p = [0.99999999999980993, 676.5203681218851, -1259.1392167224028,
+     771.32342877765313, -176.61502916214059, 12.507343278686905,
+     -0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7]
+
+def gamma(z):
+  z = complex(z)
+  # Reflection formula
+  if z.real < 0.5:
+    return pi / (sin(pi*z)*gamma(1-z))
+  else:
+    z -= 1
+    x = p[0]
+    for i in range(1, g+2):
+      x += p[i]/(z+i)
+    t = z + g + 0.5
+    return sqrt(2*pi) * t**(z+0.5) * exp(-t) * x
+
+def factorial(n):
+  return gamma(n+1)
+
+print "factorial(-0.5)**2=",factorial(-0.5)**2
+for i in range(10):
+  print "factorial(%d)=%s"%(i,factorial(i))