Re: Can't use variadic arguments to functions that use templates

[JS]

On Tuesday, 23 July 2013 at 19:14:26 UTC, H. S. Teoh wrote:

On Tue, Jul 23, 2013 at 08:54:12PM +0200, Jesse Phillips wrote:

On Tuesday, 23 July 2013 at 16:22:38 UTC, JS wrote:

>On Tuesday, 23 July 2013 at 16:15:03 UTC, Jesse Phillips >wrote:

>>On Tuesday, 23 July 2013 at 14:03:01 UTC, JS wrote:

>>>I don't think you understand(or I've already got >>>confused)...

>>>
>>>I'm trying to use B has a mixin(I don't think I made this
>>>clear). I can't use it as a normal function. e.g., I can't
>>>seem to do mixin(B(t)). If I could, this would definitely
>>>solve my problem.
>>...[Code]...
>What good does that do?
>
>What if I want to use a run-time variable in the mix?

Ah, I understand now you're interested in:

string concat(alias Data...)() { ... }

This does not exist, but maybe it should... I don't know of a
workaround to get this behavior.

Is this by any chance related to that other thread about compile-time optimized join()? 'cos if it is, I've already solved the problem via

templates:

        import std.stdio;
        
        template tuple(args...) {
                alias tuple = args;
        }
        
        /**

* Given a tuple of strings, returns a tuple in which all adjacent compile-time

         * readable strings are concatenated.
         */
        template tupleReduce(args...)
        {
                static if (args.length > 1)
                {
                        static if (is(typeof(args[0])==string) &&
                                __traits(compiles, { enum x = args[0]; }))
                        {
                                static if (is(typeof(args[1])==string) &&
                                        __traits(compiles, { enum x = args[1]; 
}))
                                {
                                        alias tupleReduce = 
tupleReduce!(args[0] ~
                                                                args[1], 
args[2..$]);
                                }
                                else
                                {
                                        alias tupleReduce = tuple!(args[0], 
args[1],
                                                                
tupleReduce!(args[2..$]));
                                }
                        }
                        else
                        {
                                alias tupleReduce = tuple!(args[0],
                                                        
tupleReduce!(args[1..$]));
                        }
                }
                else
                {
                        alias tupleReduce = args;
                }
        }
        
        void main() {
                string x = "runtime1";
                string y = "runtime2";

auto arr = [ tupleReduce!("a", "b", x, "c", "d", y, "e", "f", "g", x) ];

                writeln(arr);
        }

The output is:

        ["ab", "runtime1", "cd", "runtime2", "efg", "runtime1"]

All compile-time readable strings in the list have been concatenated at

compile-time.


T

Thanks, I'll check it out when I get a chance and report back. It
looks like it solves the problem.