added randbelow and shuffle methods

1 files changed, 26 insertions, 0 deletions

diff --git a/SyncRNG.py b/SyncRNG.py
index 7137439..7ef6fd6 100644
--- a/SyncRNG.py
+++ b/SyncRNG.py
@@ -4,11 +4,16 @@ used to seed and pull numbers from the RNG.
 
 """
 
+from __future__ import division
+
+from warnings import warn as _warn
+
 import syncrng
 
 class SyncRNG(object):
 
     def __init__(self, seed=0):
+        self.BPF = 32
         self.seed = seed
         self.state = syncrng.seed(seed)
 
@@ -19,3 +24,24 @@ class SyncRNG(object):
 
     def rand(self):
         return self.randi() * 2.3283064365387e-10
+
+    def randbelow(self, n):
+        maxsize = 1<<self.BPF
+        if n >= maxsize:
+            _warn("Underlying random generator does not supply \n"
+                    "enough bits to choose from a population range this "
+                    "large.\n")
+            return int(self.rand() * n)
+        rem = maxsize % n
+        limit = (maxsize - rem) / maxsize
+        r = self.rand()
+        while r >= limit:
+            r = self.rand()
+        return int(r*maxsize) % n
+
+    def shuffle(self, x):
+        y = x[:]
+        for i in reversed(range(1, len(y))):
+            j = self.randbelow(i+1)
+            y[i], y[j] = y[j], y[i]
+        return y