How to alter a float by its smallest increment (or close to it)?

Question

I have a double value f and would like a way to nudge it very slightly larger (or smaller) to get a new value that will be as close as possible to

Answer 1

u64 &x = *(u64*)(&f);
x++;

Yes, seriously.

Edit: As someone pointed out, this does not deal with -ve numbers, Inf, Nan or overflow properly. A safer version of the above is

u64 &x = *(u64*)(&f);
if( ((x>>52) & 2047) != 2047 )    //if exponent is all 1's then f is a nan or inf.
{
    x += f>0 ? 1 : -1;
}