What should the correct output be for the following program?

#StartFloat 20
CFunction f;
Local F = f(1.00000000000000001) + f(1.0);
Print;
.end

Currently, this produces:

   F =
      f(1.0e+00) + f(1.0e+00);

This happens because the arguments are compared in their raw internal representation: although 1.00000000000000001 and 1.0 should be indistinguishable at 20 bits of precision, the comparison occurs before rounding, and the extra limbs make them appear distinct.

This is closely related to #695 and #697.