├── .travis.yml
├── LICENSE
├── README.md
└── test.sh


/.travis.yml:
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1 | script: ./test.sh
2 | 


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/LICENSE:
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 1 | MIT License
 2 | 
 3 | Copyright (c) 2016 Sanket Dasgupta
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


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/README.md:
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  1 | # Bit Hacks
  2 | 
  3 | A collection of bit manipulation techniques.
  4 | 
  5 | *The examples are done in Python but should work with most languages
  6 |  with hardly any modification.*
  7 | 
  8 | ## Multiply a number by 2
  9 | 
 10 | ```python
 11 | >>> 5 << 1
 12 | 10
 13 | 
 14 | ```
 15 | 
 16 | ## Divide a number by 2
 17 | 
 18 | ```python
 19 | >>> 6 >> 1
 20 | 3
 21 | 
 22 | ```
 23 | 
 24 | ## Multiply by mth power of 2
 25 | 
 26 | ```python
 27 | >>> n = 5
 28 | >>> n << 3
 29 | 40
 30 | 
 31 | ```
 32 | 
 33 | ## Divide by mth power of 2
 34 | 
 35 | ```python
 36 | >>> n = 40
 37 | >>> n >> 3
 38 | 5
 39 | 
 40 | ```
 41 | 
 42 | ## Exchange two values
 43 | 
 44 | ```python
 45 | >>> x = 3
 46 | >>> y = 5
 47 | 
 48 | >>> x ^= y
 49 | >>> y ^= x
 50 | >>> x ^= y
 51 | 
 52 | >>> x
 53 | 5
 54 | >>> y
 55 | 3
 56 | 
 57 | ```
 58 | 
 59 | ## Check if an integer is even or odd
 60 | 
 61 | ```python
 62 | >>> n = 6
 63 | >>> n & 1 == 0
 64 | True
 65 | 
 66 | >>> n = 5
 67 | >>> n & 1 == 0
 68 | False
 69 | 
 70 | ```
 71 | 
 72 | ## Check Equality of two numbers
 73 | 
 74 | ```python
 75 | >>> x = 42
 76 | >>> y = 42
 77 | >>> not x ^ y
 78 | True
 79 | 
 80 | ```
 81 | 
 82 | ## Check if a number is a power of two
 83 | 
 84 | ```python
 85 | >>> n = 8
 86 | >>> n & (n-1) == 0
 87 | True
 88 | 
 89 | >>> n = 6
 90 | >>> n & (n-1) == 0
 91 | False
 92 | 
 93 | ```
 94 | 
 95 | Note that 0 is incorrectly considered a power of 2 here. To remedy this, use:
 96 | 
 97 | ```python
 98 | >>> n = 8
 99 | >>> n and not (n & (n - 1))
100 | True
101 | 
102 | ```
103 | 
104 | ## Check whether the n-th bit is set of an integer
105 | 
106 | ```python
107 | >>> n = 5
108 | >>> n & (1 << 2) > 0 # 2nd bit is set in 101 (zero-indexed).
109 | True
110 | 
111 | >>> n = 2
112 | >>> n & (1 << 2) > 0 # 2nd bit is not set 010
113 | False
114 | 
115 | ```
116 | 
117 | ## Minimum and Maximum of two numbers
118 | 
119 | ```python
120 | >>> x = 5
121 | >>> y = 2
122 | >>> y ^ ((x ^ y) & -(x < y)) # minimum
123 | 2
124 | >>> x ^ ((x ^ y) & -(x < y)) # maximum
125 | 5
126 | 
127 | ```
128 | 
129 | ## Convert integer to binary number
130 | 
131 | ```python
132 | >>> def binary(s):
133 | ...     return str(s) if s <= 1 else binary(s >> 1) + str(s & 1)
134 | >>> binary(28)
135 | '11100'
136 | 
137 | ```
138 | 
139 | ## Resources
140 | 
141 | * [awesome-bits](https://github.com/keon/awesome-bits)
142 | * [A Bit of Fun: Fun with Bits - Topcoder](https://www.topcoder.com/community/data-science/data-science-tutorials/a-bit-of-fun-fun-with-bits/)
143 | * [Bit Manipulation - HackerEarth](https://www.hackerearth.com/practice/notes/bit-manipulation/)
144 | * [Bit Twiddling Hacks - Stanford](https://graphics.stanford.edu/~seander/bithacks.html)
145 | 


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/test.sh:
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1 | #!/usr/bin/env bash
2 | python -m doctest -v README.md
3 | 


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