Hi!
Tell me please,are there any way to check whether number is NaN?

Zhenya:

> Tell me please,are there any way to check whether number is NaN?

http://dlang.org/phobos/std_math.html#isNaN

Bye,
bearophile

On Friday, 28 December 2012 at 15:59:35 UTC, bearophile wrote:
> Zhenya:
>
>> Tell me please,are there any way to check whether number is NaN?
>
> http://dlang.org/phobos/std_math.html#isNaN
>
> Bye,
> bearophile

Thank you!

>
>> Tell me please,are there any way to check whether number is NaN?
>
> http://dlang.org/phobos/std_math.html#isNaN
>


pure nothrow @trusted bool isNaN(real x);

Returns !=0 if e is a NaN.

-------------------
Seems like a slight documentation disagreement. Shows bool prototype but description says returns !=0

On 2012-42-28 16:12, Zhenya <zheny@list.ru> wrote:

> Hi!
> Tell me please,are there any way to check whether number is NaN?

us std.math.isNaN. But if you really don't want to:

float x = ...;

if (x != x) {
    writeln( "x is NaN" );
}

I'm unsure how aggressive the optimizer is allowed to be in cases
like this. Theoretically it could assume x is always equal to x,
but I'd think it's not allowed to for floats.

If you're wondering how a float value could compare different to
the exact same value, consider that this would otherwise be true:

sqrt(-1) == 0/0

-- 
Simen

On Friday, 28 December 2012 at 20:19:49 UTC, Simen Kjaeraas wrote:
> On 2012-42-28 16:12, Zhenya <zheny@list.ru> wrote:
>
>> Hi!
>> Tell me please,are there any way to check whether number is NaN?
>
> us std.math.isNaN. But if you really don't want to:
>
> float x = ...;
>
> if (x != x) {
>     writeln( "x is NaN" );
> }
>
> I'm unsure how aggressive the optimizer is allowed to be in cases
> like this. Theoretically it could assume x is always equal to x,
> but I'd think it's not allowed to for floats.
>
> If you're wondering how a float value could compare different to
> the exact same value, consider that this would otherwise be true:
>
> sqrt(-1) == 0/0

Thank you,understood)
It's a nice way.