How to check for instantiation of specific template?
Jacob Carlborg
doob at me.com
Fri Oct 11 00:56:39 PDT 2013
On 2013-10-10 19:23, H. S. Teoh wrote:
> I have a template used for storing compile-time values:
>
> template Def(int x, string y) {
> alias impl = TypeTuple!(x,y);
> }
>
> How do I define a template isDef that, given some template alias A,
> evaluates to true if A is some instantiation of Def?
>
> template isDef(alias A) {
> enum A = ... /* what to put here? */
> }
>
> The intent is to be able to write signature constraints like this:
>
> auto myFunc(alias def)(...)
> if (isDef!def)
> {
> ...
> }
>
> ...
> // Pass an instantiation of Def to myFunc
> auto x = myFunc!(Def!(1, "abc"))(args);
>
> I tried using std.traits.isInstanceOf but apparently it expects the
> second argument to be an actual type, which doesn't work in this case
> because Def is a typetuple of compile-time values, not an actual type.
I found this old thread
http://forum.dlang.org/thread/mailman.1382.1371938670.13711.digitalmars-d@puremagic.com
With this code:
template getTemplate(alias T : TI!TP, alias TI, TP...)
{
alias getTemplate = TI;
}
But I haven't figured out how to do the comparison.
--
/Jacob Carlborg
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