Typed variadic template syntax?

[Idan Arye]

On Thursday, 30 January 2014 at 14:08:27 UTC, Ilya Yaroshenko 
wrote:
> 1) You can use 
> mixin(format("<Prolog>%(<Begin>%s<End>%)<Epilog>", 
> CompileTimeRange)); See std.format for ranges and 
> std.string.format.

That works for simple cases. Complex cases require that you write 
a function and calling it with CTFE for creating the mixin 
string. This can be a problem outside functions, because you are 
polluting the namespace. It might not be that bad for structs and 
classes, since you can simply make that helper function private - 
but for template mixins the helper function must be exposed to 
the code that uses the mixin.

Having complex strings mixing also means that if there is a 
problem in that string, the compiler will point to the line where 
the string is mixed in, not the one where the code that 
introduces the error is concentrated to the string. Having a 
static foreach will make the string mixins small and simple 
enough for this to not be a problem.

Metaprogramming by building the code strings is not something 
that should be encouraged(*cough* C macros *cough*), but it's 
currently required sometimes for complex metaprogramming in D. If 
we had static foreach we would still need string mixins, but at 
least we will be mixing in many small simple strings instead of 
one big complex string, and that means we could add to Phobos 
some helper template mixins for sanitizing the arguments for 
those mixins.