Rule 13.3 with respect to 0.0

[gs]

Does rule 13.3 permit testing a floating point expression against 0.0?

Code:

void f( float flt )
{
if( flt == 0.0 )
    {}
}

If not, how is this test any different than

Code:

void f( float flt )
{
if( !flt )
    {}
}

?

Or does 13.3 not permit the second example either?