Comparing IEEE floats and doubles for equality

Question

What is the best method for comparing IEEE floats and doubles for equality? I have heard of several methods, but I wanted to see what the community thought.

Answer 1

The current version I am using is this

bool is_equals(float A, float B,
               float maxRelativeError, float maxAbsoluteError)
{

  if (fabs(A - B) < maxAbsoluteError)
    return true;

  float relativeError;
  if (fabs(B) > fabs(A))
    relativeError = fabs((A - B) / B);
  else
    relativeError = fabs((A - B) / A);

  if (relativeError <= maxRelativeError)
    return true;

  return false;
}

This seems to take care of most problems by combining relative and absolute error tolerance. Is the ULP approach better? If so, why?