Does D support nested Templates aka Higher Kinded Polymorphism?
Jerry
Kickupx at gmail.com
Tue Oct 3 13:02:10 UTC 2017
On Tuesday, 3 October 2017 at 12:58:47 UTC, sighoya wrote:
> On Tuesday, 3 October 2017 at 12:09:04 UTC, rikki cattermole
> wrote:
>> On 03/10/2017 1:05 PM, sighoya wrote:
>>> Especially, I mean something like
>>>
>>> T<S> foo(S,T)(T<S> i)
>>> {
>>> ...
>>> }
>>
>> struct Foo(T) {
>> T value;
>> }
>>
>> T!S foo(S, alias T)(T!S v) { return v; }
>>
>>
>> void main() {
>> import std.stdio;
>> writeln(foo!(int, Foo)(Foo!int(1)));
>> }
>
> Cool, but it seems that only a nesting of two is allowed, right?
> This one gives an error:
>
> T!S!R bar(alias T,alias S,R)(T!S!R v) {return v;}
> Error: multiple ! arguments are not allowed
That is because you have to wrap multiple with ().
Use
T!(S!R)
instead.
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