Merge pull request #309 from MonliH/patch-1

Added a calculate PI function

Author: geekcomputers

primelib/primelib.py

@@ -38,6 +38,25 @@
 goldbach(number)  // Goldbach's assumption
 
 """
+def pi(maxK=70, prec=1008, disp=1007):
+    """
+    maxK: nuber of iterations
+    prec: precision of decimal places
+    disp: number of decimal places shown
+    """
+    from decimal import Decimal as Dec, getcontext as gc
+    gc().prec = prec
+    K, M, L, X, S = 6, 1, 13591409, 1, 13591409 
+    for k in range(1, maxK+1):
+        M = Dec((K**3 - (K<<4)) * M / k**3)
+        L += 545140134
+        X *= -262537412640768000
+        S += Dec(M * L) / X
+        K += 12
+    pi = 426880 * Dec(10005).sqrt() / S
+    pi = Dec(str(pi)[:disp])
+    return pi
+
 
 def isPrime(number):
     """
@@ -602,4 +621,4 @@ def fib(n):
         ans += fib1
         fib1 = tmp
 
-    return ans
+    return ans