Bug?

[deed via Digitalmars-d-learn]

> Using equality is not a good idea with floating point.
>
> The compiler will on a whim, or depending on whether it can 
> inline or not, use higher precision floats, changing the 
> outcome slightly.
>
> I cannot say for certain whether this explains all the issues 
> you have, the very last one seems troubling to me at least.
>
> -Steve

Sure, in many cases it's a bad idea. While I understand that 
sin(PI) != 0.0, but approxEqual(sin(PI), 0.0) == true, I would 
expect the following to pass:

assert (0.0 == 0.0);
assert (1.2345 == 1.2345);

F a = 1.2345, b = 9.8765;

assert (a+b == b+a);
assert (a*b == b*a);

F fun (F a) pure;

assert (fun(a) + fun(b) == fun(b) + fun(a));
assert (fun(a) * fun(b) == fun(b) * fun(a));

auto a = fun(100);
auto b = fun(100);

assert (a == b);
assert (fun(100) == fun(100));


Now, if fun's body is { return sin(a); }, the behaviour changes 
to:

auto c = fun(100);
auto d = fun(100);

assert (c == d);              // Ok
assert (fun(100) != fun(100)) // I have a hard time understanding
                               // this is correct behaviour