On 05/26/2016 05:28 PM, ArturG wrote:
> On Thursday, 26 May 2016 at 15:25:26 UTC, ag0aep6g wrote:
[...]
>> What does it matter?
>
> You would have to create special cases for them.

When? If you want to check if something is the .init value, compare against .init.

On Thursday, 26 May 2016 at 15:38:55 UTC, Basile B. wrote:

>
> because nan is not 0 and that the shortcut for float is
>
> if (fpValue) <=> if (fpValue != 0)
> if (!fpValue)<=> if (fpValue == 0)
>
> There's no relation between the initializer and the shortcut. It's not because for some values the shortcut matches to the initializer that it must always be the case...But I admit I don't know the exact rationale.
>
> Does anyone know ?

Ok sorry for the noise and thanks anyway.

On Thursday, 26 May 2016 at 15:34:50 UTC, ArturG wrote:
> On Thursday, 26 May 2016 at 15:29:52 UTC, Basile B. wrote:
>
>>
>> float.init is not equal to 0.0f. In D FP points values are initialized to nan (not a number).
>>
>> By the way for strings it works, it's like the array case I described in the first answer).
>
> yes i guess i tested all/most types and know that float.init is float.nan but why is nan true and not false?

Oh, I'm so sorry ! I totally missed the point of the Q.

float.nan is not a "unique" value. Several values verify "nan" (Look at std.math.isNan). So I suppose it's simpler to test for nullity. Though with the sign there's also two possible 0...

On Thursday, 26 May 2016 at 15:48:18 UTC, Basile B. wrote:
> On Thursday, 26 May 2016 at 15:34:50 UTC, ArturG wrote:
>> On Thursday, 26 May 2016 at 15:29:52 UTC, Basile B. wrote:
>>
>>>
>>> float.init is not equal to 0.0f. In D FP points values are initialized to nan (not a number).
>>>
>>> By the way for strings it works, it's like the array case I described in the first answer).
>>
>> yes i guess i tested all/most types and know that float.init is float.nan but why is nan true and not false?
>
> Oh, I'm so sorry ! I totally missed the point of the Q.
>
> float.nan is not a "unique" value. Several values verify "nan" (Look at std.math.isNan). So I suppose it's simpler to test for nullity. Though with the sign there's also two possible 0...

void main(string[] args)
{
    writeln(float.nan == float.init); // false
    import std.math: isNaN;
    writeln(isNaN(float.nan));  // true
    writeln(isNaN(float.init)); //true
}

So the shortcut in the compiler might be more simple, there is only a single test for "if(myFloat)"...

On Thursday, 26 May 2016 at 15:51:39 UTC, Basile B. wrote:

>> Oh, I'm so sorry ! I totally missed the point of the Q.
>>
>> float.nan is not a "unique" value. Several values verify "nan" (Look at std.math.isNan). So I suppose it's simpler to test for nullity. Though with the sign there's also two possible 0...
>
> void main(string[] args)
> {
>     writeln(float.nan == float.init); // false
>     import std.math: isNaN;
>     writeln(isNaN(float.nan));  // true
>     writeln(isNaN(float.init)); //true
> }
>
> So the shortcut in the compiler might be more simple, there is only a single test for "if(myFloat)"...

im just playing with this template[1] is there anything else i missed? (if you dont mind)
it basically treats any T.init as false and skips the function/delegate and just returns type.

[1] https://dpaste.dzfl.pl/d159d83e3167

On Thursday, 26 May 2016 at 16:45:22 UTC, ArturG wrote:
> im just playing with this template[1] is there anything else i missed? (if you dont mind)
> it basically treats any T.init as false and skips the function/delegate and just returns type.
>
> [1] https://dpaste.dzfl.pl/d159d83e3167

If you just want to check whether something is equal to its type's .init value, use the `is` operator, which does a bitwise comparison:

    if(value is typeof(value).init) ...

On Friday, 27 May 2016 at 09:25:55 UTC, Marc Schütz wrote:
> On Thursday, 26 May 2016 at 16:45:22 UTC, ArturG wrote:
>> im just playing with this template[1] is there anything else i missed? (if you dont mind)
>> it basically treats any T.init as false and skips the function/delegate and just returns type.
>>
>> [1] https://dpaste.dzfl.pl/d159d83e3167
>
> If you just want to check whether something is equal to its type's .init value, use the `is` operator, which does a bitwise comparison:
>
>     if(value is typeof(value).init) ...

that still requiers a special case for floating points, arrays and optionally empty string literals.

On Friday, 27 May 2016 at 14:43:47 UTC, ArturG wrote:
>>     if(value is typeof(value).init) ...
>
> that still requiers a special case for floating points, arrays and optionally empty string literals.

Have you tried? That should work in all cases.

On Friday, 27 May 2016 at 14:48:59 UTC, Adam D. Ruppe wrote:
> On Friday, 27 May 2016 at 14:43:47 UTC, ArturG wrote:
>>>     if(value is typeof(value).init) ...
>>
>> that still requiers a special case for floating points, arrays and optionally empty string literals.
>
> Have you tried? That should work in all cases.

   float f;
   if(f is float.init) "float init".writeln;
   f = float.nan;
   if(f is float.init) "float nan".writeln;

On Friday, 27 May 2016 at 14:56:28 UTC, ArturG wrote:
>    float f;
>    if(f is float.init) "float init".writeln;
>    f = float.nan;
>    if(f is float.init) "float nan".writeln;

You changed it to a value that isn't float.init, so of course it isn't going to match!

float.nan and float.init are NOT the same thing. float.init is a kind of NAN, but not the same kind.