• Sjoerd Nijboer (41/41) Jul 14 2019 I am trying to create a template function with a switch case
• Adam D. Ruppe (19/37) Jul 14 2019 I'd probably just do
• Sjoerd Nijboer (14/19) Jul 15 2019 I eventually went with

Sjoerd Nijboer <dlang sjoerdnijboer.com> writes:

I am trying to create a template function with a switch case 
inside it.
The function signature is:
`static void doSwitch(T...)(int i)`

The code it must generate for `doSwitch!(foo, bar)()` is
`{
     switch (int)
     {
         foo:
             foo();
             return;
         bar:
             bar();
             return;
     }
}`

It would be nice if this function would cast `i` to an enum too 
so that I can put down a breakpoint in a debugger and maybe add 
some logging, but that is not strictly neccesary.


The code I have right now is:
`
template switchEnum(FunctionNames...)
{
     enum temp = [FunctionNames].join(", ");

     enum switchEnum = "{" ~ temp ~ "};";
}

static void doSwitch(FunctionNames...)(int i)
{
     auto functionName = cast(switchEnum!FunctionNames) i;

     switch (functionName)
     {
         static foreach (name; FunctionNames)
         {
             name ~ " : " ~ name ~ "(); break;";
         }
     }
}
`
But I can't get it to work and am hitting a dead end.
The error I get:
`Error: switchEnum!(foo, bar) is used as a type`

Adam D. Ruppe <destructionator gmail.com> writes:

On Sunday, 14 July 2019 at 19:26:41 UTC, Sjoerd Nijboer wrote:
 The code it must generate for `doSwitch!(foo, bar)()` is
 `{
     switch (int)
     {
         foo:
             foo();
             return;
         bar:
             bar();
             return;
     }
 }`

I'd probably just do

void doSwitch(items...)(int i) {
    switch(i) {
       static foreach(idx, item; items) {
          case idx:
              item();
              return;
       }
    }
}


That should work pretty simply.

     enum temp = [FunctionNames].join(", ");

     enum switchEnum = "{" ~ temp ~ "};";

Were you trying to do a mixin here? The error you mention below 
is trying to use this switchEnum thing as a type... and it isn't 
a type, it is just a string. the mixin() is necessary to compile 
it into code and thus create that type.

mixin("enum switchEnum = { " ~ temp ~ "}");

but I think even attempting this is overcomplicating.

         static foreach (name; FunctionNames)
         {
             name ~ " : " ~ name ~ "(); break;";
         }

ditto down here too.

Sjoerd Nijboer <dlang sjoerdnijboer.com> writes:

On Sunday, 14 July 2019 at 19:59:36 UTC, Adam D. Ruppe wrote:
 but I think even attempting this is overcomplicating.

         static foreach (name; FunctionNames)
         {
             name ~ " : " ~ name ~ "(); break;";
         }


I eventually went with

`switch (mixin(index))
{
     static foreach (index, name; FunctionNames)
     {
         mixin(index) ~ " : " ~ mixin(name) ~ "(); break;";
     }
     default:
         throw new Exception("Out of range.");
}`

I also ditched the idea of an enum for now, but I might add 
something simular in later for logging purposes.
Thank you for your help!