Logo

Programming-Idioms

This language bar is your friend. Select your favorite languages!
  • Fortran

Idiom #85 Check if integer addition will overflow

Write boolean function addingWillOverflow which takes two integers x, y and return true if (x+y) overflows.

An overflow may be above the max positive value, or below the min negative value.

  logical function adding_will_overflow (x,y) result(res)
    integer, intent(in) :: x, y
    res = (x > 0 .and. y > huge(x) - x) .or. (x < 0 .and. y < huge(x) - x)
  end function adding_will_overflow
function Adding_Will_Overflow (X, Y : Integer) return Boolean is
begin
   return X > 0 and Y > 0 and X > Integer'Last - Y;
end Adding_Will_Overflow;

PROBLEM: this doesn't detect negative overflow.

New implementation...
< >
deleplace