Functions that do bit operations.

jwasham · jwasham · commit 07720bb9161f · 2016-06-24T19:21:25.000-07:00
diff --git a/bit_manipulation/bits.py b/bit_manipulation/bits.py
@@ -9,12 +9,60 @@ def hamming_distance(x, y):
     return count
 
 
+def hamming_weight(x):
+    count = 0
+    while x != 0:
+        count += 1
+        x &= x - 1
+    return count
+
+
+def is_bit_set(bitfield, pos):
+    return (bitfield & (1 << pos)) != 0
+
+
+def is_even(x):
+    return x & 1 == 0
+
+
+def is_power_of_2(x):
+    return (x & x - 1) == 0
+
+
+# Returns the n bits in bitfield starting at position pos
+def get_bits(bitfield, pos, n):
+    return (bitfield >> (pos + 1 - n)) & ~(~0 << n)
+
+
 def main():
     # for x in range(0, 20):
     #     print(x, bin(x), hex(x))
 
     print("Hamming distance: 1010111100 and 1001010101: ", hamming_distance(0b1010111100, 0b1001010101))
 
+    print("Bit 0: 1011 1100 set?", is_bit_set(0b10111100, 0))
+    print("Bit 1: 1011 1100 set?", is_bit_set(0b10111100, 1))
+    print("Bit 2: 1011 1100 set?", is_bit_set(0b10111100, 2))
+    print("Bit 3: 1011 1100 set?", is_bit_set(0b10111100, 3))
+    print("Bit 4: 1011 1100 set?", is_bit_set(0b10111100, 4))
+    print("Bit 5: 1011 1100 set?", is_bit_set(0b10111100, 5))
+    print("Bit 6: 1011 1100 set?", is_bit_set(0b10111100, 6))
+    print("Bit 7: 1011 1100 set?", is_bit_set(0b10111100, 7))
+
+    print("Hamming weight: 1010111100:", hamming_weight(0b1010111100))
+    print("Hamming weight: 1001000001:", hamming_weight(0b1001000001))
+    print("Hamming weight: 0001000000:", hamming_weight(0b0001000000))
+    print("Hamming weight: 0000000000:", hamming_weight(0b0000000000))
+    print("Hamming weight: 11111111:", hamming_weight(0b11111111))
+
+    for x in range(0, 5):
+        print(str(x) + " is even?", is_even(x))
+
+    for x in range(0, 17):
+        print(str(x) + " is power of 2?", is_power_of_2(x))
+
+    print("Get 3 bits starting at position 5 in 1010111100", bin(get_bits(0b1010111100, 5, 3)))
+    print("Get 3 bits starting at position 8 in 1010111100", bin(get_bits(0b1010111100, 9, 3)))
 
 if __name__ == "__main__":
     main()
