compile time method check

[Bill Baxter]

2008/12/27 Weed <resume755 at mail.ru>:
> Simen Kjaeraas пишет:
>> On Fri, 26 Dec 2008 20:15:30 +0100, Weed <resume755 at 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