parameter pack to inputRange

[Ali Çehreli via Digitalmars-d-learn]

On 05/08/2016 04:48 PM, Erik Smith wrote:
> On Sunday, 8 May 2016 at 22:37:44 UTC, Dicebot wrote:
>> On Sunday, 8 May 2016 at 14:11:31 UTC, Ali Çehreli wrote:
>>>         E front() {
>>>             final switch (index) {
>>>                 /* static */ foreach (i, arg; Args) {
>>>                     case i:
>>>                         return arg;
>>>                 }
>>>             }
>>>         }
>>
>> AFAIK, this will do funny things with referencing stack if arguments
>> are variables and not literals.
>
> Thanks! The static array version works for me too.   It would be good to
> understand more about what is going on.  It looks like the cost of the
> static array is an extra copy for each element. Maybe there is still a
> way to avoid that.
>

I had to change one line of your test code. Dicebot's code work with it:

auto toInputRange (T...) (T args) @nogc
{
     import std.traits : CommonType;
     alias E = CommonType!T;

     struct Range
     {
         E[T.length] args;
         size_t index;

         E front () { return args[index]; }
         void popFront () { ++index; }
         bool empty () { return index >= args.length; }
     }

     Range range;
     foreach (i, ref arg; args)
         range.args[i] = arg;
     return range;
}

static void foo(Args...)(Args args) {
     import std.container.array;
     auto array = Array!int(toInputRange(args));  // <-- HERE

     foreach(a; array) {
         import std.stdio : writeln;
         writeln("e: ", a);
     }
}

void main ( )
{
     import std.stdio;
     writeln(toInputRange(1, 2, 3));

     foo(1,2,3);
}

It used to be

     toInputRange!(args)

Ali