• =?UTF-8?B?Tm9yZGzDtnc=?= (1/1) Jan 15 2016 How do I index a function parameter tuple with a run-time index?
• anonymous (22/23) Jan 15 2016 With a switch and a static foreach:
• Meta (3/27) Jan 15 2016 And of course I'm proven wrong as soon as I post :) Sometimes I
• Justin Whear (2/4) Jan 15 2016 Username doesn't check out, :(
• Meta (2/6) Jan 15 2016 Huh?
• Meta (6/7) Jan 15 2016 I believe it's impossible because a parameter tuple is not a

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

How do I index a function parameter tuple with a run-time index?

anonymous <anonymous example.com> writes:

On 15.01.2016 21:42, Nordlöw wrote:
 How do I index a function parameter tuple with a run-time index?

With a switch and a static foreach:

----
void f(A...)(size_t i, A a)
{
     import std.stdio: writeln;
     switch_: switch (i)
     {
         foreach (iT, T; A)
         {
             case iT: writeln(T.stringof); break switch_;
         }
         default: writeln("??"); break;
     }
}

void main()
{
     f(0, "foo", 42); /* string */
     f(1, "foo", 42); /* int */
     f(2, "foo", 42); /* ?? */
}
----

Meta <jared771 gmail.com> writes:

On Friday, 15 January 2016 at 20:48:39 UTC, anonymous wrote:
 On 15.01.2016 21:42, Nordlöw wrote:
 How do I index a function parameter tuple with a run-time 
 index?

 With a switch and a static foreach:

 ----
 void f(A...)(size_t i, A a)
 {
     import std.stdio: writeln;
     switch_: switch (i)
     {
         foreach (iT, T; A)
         {
             case iT: writeln(T.stringof); break switch_;
         }
         default: writeln("??"); break;
     }
 }

 void main()
 {
     f(0, "foo", 42); /* string */
     f(1, "foo", 42); /* int */
     f(2, "foo", 42); /* ?? */
 }
 ----

And of course I'm proven wrong as soon as I post :) Sometimes I 
forget how powerful D's  code generation abilities are.

Justin Whear <justin economicmodeling.com> writes:

On Fri, 15 Jan 2016 20:52:46 +0000, Meta wrote:

 And of course I'm proven wrong as soon as I post :) Sometimes I forget
 how powerful D's  code generation abilities are.

Username doesn't check out, :(

Meta <jared771 gmail.com> writes:

On Friday, 15 January 2016 at 21:47:21 UTC, Justin Whear wrote:
 On Fri, 15 Jan 2016 20:52:46 +0000, Meta wrote:

 And of course I'm proven wrong as soon as I post :) Sometimes 
 I forget how powerful D's  code generation abilities are.

 Username doesn't check out, :(

Huh?

Meta <jared771 gmail.com> writes:

On Friday, 15 January 2016 at 20:42:47 UTC, Nordlöw wrote:
 How do I index a function parameter tuple with a run-time index?

I believe it's impossible because a parameter tuple is not a 
runtime entity. If it was an expression tuple (a compile-time 
tuple of only values, no types or symbols) and all of the values 
had a common base type, you could put it in an array and index 
that.