Can I at compile time check whether there is a facility method
(toString(), for example)?

Today I wrote:

                static if ( __traits(isArithmetic, Element) ) {
                    ret ~= toString(this[i,j]) ~ "\t";
                } else {
                    ret ~= this[i,j].toString ~ "\t";
                }

It works but it is wrong

On Fri, 26 Dec 2008 20:15:30 +0100, Weed <resume755@mail.ru> wrote:

> Can I at compile time check whether there is a facility method
> (toString(), for example)?
>
> Today I wrote:
>
>                 static if ( __traits(isArithmetic, Element) ) {
>                     ret ~= toString(this[i,j]) ~ "\t";
>                 } else {
>                     ret ~= this[i,j].toString ~ "\t";
>                 }
>
> It works but it is wrong

I believe this works:

static if (is(typeof(this[i,j].toString))) {
	ret ~= this[i,j].toString;
} else {
	ret ~= toString(this[i,j]);
}

-- 
Simen

On Sat, Dec 27, 2008 at 6:30 AM, Simen Kjaeraas <simen.kjaras@gmail.com> wrote:
> On Fri, 26 Dec 2008 20:15:30 +0100, Weed <resume755@mail.ru> wrote:
>
>> Can I at compile time check whether there is a facility method
>> (toString(), for example)?
>>
>> Today I wrote:
>>
>>                static if ( __traits(isArithmetic, Element) ) {
>>                    ret ~= toString(this[i,j]) ~ "\t";
>>                } else {
>>                    ret ~= this[i,j].toString ~ "\t";
>>                }
>>
>> It works but it is wrong
>
> I believe this works:
>
> static if (is(typeof(this[i,j].toString))) {
>        ret ~= this[i,j].toString;
> } else {
>        ret ~= toString(this[i,j]);
> }
>

Additionally, in D2 I think you can do this:   __traits(compiles,
this[i,j].toString)

--bb

2008/12/27 Weed <resume755@mail.ru>:
> Simen Kjaeraas пишет:
>> On Fri, 26 Dec 2008 20:15:30 +0100, Weed <resume755@mail.ru> wrote:
>>
>>> Can I at compile time check whether there is a facility method
>>> (toString(), for example)?
>>>
>>> Today I wrote:
>>>
>>>                 static if ( __traits(isArithmetic, Element) ) {
>>>                     ret ~= toString(this[i,j]) ~ "\t";
>>>                 } else {
>>>                     ret ~= this[i,j].toString ~ "\t";
>>>                 }
>>>
>>> It works but it is wrong
>>
>> I believe this works:
>>
>> static if (is(typeof(this[i,j].toString))) {
>>     ret ~= this[i,j].toString;
>> } else {
>>     ret ~= toString(this[i,j]);
>> }
>>
>
> No, this cause error:
>
> toString () does not match parameter types (float)
>
> ( condition is always resolved to else {...} )

That's because float's don't have a toString method.  So it should be picking the else{} case.

If you try it with something where this[i,j] returns an Object or struct with a toString, then it should pick the 'if' branch.

--bb

Bill Baxter пишет:
> 2008/12/27 Weed <resume755@mail.ru>:
>> Simen Kjaeraas пишет:
>>> On Fri, 26 Dec 2008 20:15:30 +0100, Weed <resume755@mail.ru> wrote:
>>>
>>>> Can I at compile time check whether there is a facility method
>>>> (toString(), for example)?
>>>>
>>>> Today I wrote:
>>>>
>>>>                 static if ( __traits(isArithmetic, Element) ) {
>>>>                     ret ~= toString(this[i,j]) ~ "\t";
>>>>                 } else {
>>>>                     ret ~= this[i,j].toString ~ "\t";
>>>>                 }
>>>>
>>>> It works but it is wrong
>>> I believe this works:
>>>
>>> static if (is(typeof(this[i,j].toString))) {
>>>     ret ~= this[i,j].toString;
>>> } else {
>>>     ret ~= toString(this[i,j]);
>>> }
>>>
>> No, this cause error:
>>
>> toString () does not match parameter types (float)
>>
>> ( condition is always resolved to else {...} )
> 
> That's because float's don't have a toString method.  So it should be picking the else{} case.
> 
> If you try it with something where this[i,j] returns an Object or struct with a toString, then it should pick the 'if' branch.


There was confusion between this.toString () and std.stdio.toString ()

Fixed, thanks!