Greatest common divisor

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Task

Find the greatest common divisor   (GCD)   of two integers.


Greatest common divisor   is also known as   greatest common factor (gcf)   and   greatest common measure.



Related task

   least common multiple.


See also

   MathWorld entry:   greatest common divisor.
   Wikipedia entry:     greatest common divisor.


const func integer: gcd (in var integer: a, in var integer: b) is func
  result
    var integer: gcd is 0;
  local
    var integer: help is 0;
  begin
    while a <> 0 do
      help := b rem a;
      b := a;
      a := help;
    end while;
    gcd := b;
  end func;