On 06/06/2012 10:02 AM, Jonathan Crapuchettes wrote:
> I'm running into a problem with the following function definition when
> passing in a const(string[]).
>
> public T condenseCountyList(T)(const T inputList) if (is(Unqual!T :
> string) || is(Unqual!T : string[]))
>
> I'm getting the "Error: template common.condenseCountyList does not
> match any function template declaration" when calling the function as
>
> condenseCountyList(countyList);
>
> , but if I changed the calling code to
>
> condenseCountyList(cast(string[])countyList)
>
> dmd is happy.
>
> How do I need to change the function constraint to make this work?
>
> Thank you,
> Jonathan Crapuchttes
Sorry for being terse but this works:
import std.traits;
import std.array;
template isSomeStringArray(T)
{
enum isSomeStringArray = is (typeof(
{
T variable;
static assert (isSomeString!(typeof(variable.front)));
}()));
}
T condenseCountyList(T)(const T inputList)
if (isSomeString!T || isSomeStringArray!T)
{
return T.init;
}
void main()
{
auto countyList = [ "Santa Clara" ];
condenseCountyList(countyList);
}
isSomeString is defined in std.traits. isSomeStringArray above uses a
number of D features:
* anonymous delegate
* executing that delegate by () (which is actually never executed)
* typeof, which produces "invalid type" if the expression illegal
* is, which produces true if the type that it receives is not invalid
* eponymous templates
Ali
--
D Programming Language Tutorial: http://ddili.org/ders/d.en/index.html
