Can [] be made to work outside contexts of binary operators?

[Idan Arye via Digitalmars-d]

On Thursday, 22 October 2015 at 15:57:05 UTC, Shriramana Sharma 
wrote:
> I tried:
>
> import std.stdio;
> void main()
> {
> 	int [5] vals = [1, 2, 3, 4, 5];
> 	writefln("A = %d, B = %d, C = %d, D = %d, E = %d", vals []);
> }
>
> but got thrown an exception that "%d is not a valid specifier 
> for a range".
>
> The Python equivalent to flatten a list works:
>
> vals = [1, 2, 3, 4, 5]
> print("A = {}, B = {}, C = {}, D = {}, E = {}".format(*vals))
>
> Output:
>
> A = 1, B = 2, C = 3, D = 4, E = 5
>
> Question:
>
> Can D's [] be made to work that way? I recently had to write 
> custom functions since I had an array representing numerical 
> fields and wanted to print them out with individual labels but 
> I wasn't able to use a single writefln with sufficient 
> specifiers for that purpose because of this limitation.

D's `writefln` is a template-variadic function. Each time you use 
it, the compiler looks at the arguments you send to it, and 
compiles a new instantiation of it based on the number and types 
of these arguments. This means that it would have to know at 
compile time how many values `vals[]` holds - but that number is 
only known at runtime!

Now, in your case, since vals is a static array, it should be 
possible to know it's value at compile time. Maybe if there was a 
`tupleof` for static arrays?

At any rate, you can always use the range formatters %( and %) to 
print the array. See http://dpaste.dzfl.pl/47e3e5a9e5c4