# XGCD --- greatest common divisor
  #
  # xgcd(a,b) = greatest common divisor of a and b
  #
  # assume that a and b are positive integers
  #


  xgcd := proc(b,a)
        local r;     
        r := b mod a;
        # print(b,a,r);
        if r = 0 
           then RETURN(a);
           else xgcd(a,r);
        fi;
  end:

  # jac, 6/11/2001