On 10/23/14 2:18 PM, deed wrote:
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.
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);
None of these fail on my system
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));
Not sure what body of fun is, so I cannot test this.
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
Tried that out, it does not fail on my machine. Can you be more specific
on your testing? What compiler/platform? Stock compiler, or did you
build it yourself?
-Steve
