Re: Passing anonymous templated functions as template parameters

[Basile B. via Digitalmars-d-learn]

On Wednesday, 15 June 2016 at 23:52:56 UTC, Basile B. wrote:
On Wednesday, 15 June 2016 at 22:27:38 UTC, pineapple wrote:
Here's a simple code example to illustrate what I expected to 
work and didn't - is this a mistake in my syntax or a 
limitation of the language?

    template SomeTemplate(alias func){
        auto templatefunc(T)(int x){
            return func!T(x);
        }
    }

    // Valid
    auto somefunc(T)(int x){
        return cast(T) x;
    }
    alias fn1 = SomeTemplate!somefunc;

    // Not valid
    alias fn2 = SomeTemplate!(
        (T)(int x){return cast(T) x;}
    );

This syntax passes:

    alias fn2(T) = SomeTemplate!((int x){return cast(T) x;});

I didn't try to instanciate previously. It works a bit with a 
lambda to the
extent that the alias has the template parameter list.

import std.stdio;

template A(alias func)
{
    auto a(T)(int x)
    {
        return func!T(x);
    }
}

alias spec(T) = A!(x => (cast(T) x));

void main(string[] args)
{
    writeln((spec!byte).a!int(257)); // 1
}