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CppBitShifting

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(C++) Bit shifting

Quick technique for dividing and multiplying numbers.

include <cassert>


int main()
{
  const int value1 = 64;
  int value2 = value1>>=1;
  value2>>=1; //Shift the bits of 64 to the right
  assert(value2 == 32);
}

Biological example

From http://richelbilderbeek.nl/CppInheritance.htm:

Code snippet of a function to convert an integer to a std::string of zeroes and ones. Also it shows an example of bitwise manipulation often used in biology: If the genome of a kid's offspring consists of 0's and 1's only, then you only need one integer to generate to offspring's genome.

include <iostream>

include <string>


std::string intToBitString(int bits)
{
  std::string s;
  if (bits==0) return "00000000";
  while (bits>0)
  {
    s = (bits % 2 ? "1" : "0") + s;
    bits>>=1;
  }
  while (s.size() % 8) { s = "0" + s; }
  return s;
}
int main()
{
  const int mother  = 15;  //00001111
  const int father  = 240; //11110000
  const int inherit = 170; //10101010 ---> 0 denotes: inherits from mother, 1: inherits from father
  //Results should be        10100101
  const int kid = (mother & (~inherit)) | (father & inherit);
  std::cout << intToBitString(mother) << std::endl;
  std::cout << intToBitString(father) << std::endl;
  std::cout << intToBitString(inherit) << std::endl;
  std::cout << intToBitString(kid) << std::endl;
}

Code links

• assert
• char
• cout
• endl
• int
• iostream
• main
• rand
• return
• std

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