Using a tuple as a function parameter

[monkyyy]

On Friday, 22 November 2024 at 16:36:43 UTC, Andrew wrote:
> I'm getting started using D for some small personal projects 
> and one thing I wanted to do was use a helper function for a 
> tuple. I declared the function like this:
>
>     string getOrZeroth(Tuple!(string, string, string) tup, int 
> i) pure {
>         return tup[i] == "" ? tup[0] : tup[i];
>     }
>
> and would like to use it like this:
>
>     auto foo = tuple("a", "", "c");
>     writeln(foo.getOrZeroth(1)); // prints a
>
> but when I try it, I'm getting the below error:
>
>> Error: variable \`i\` cannot be read at compile time
>
> It would probably make more sense to create a class and make 
> that a member function, but at this point I'm mostly just 
> curious about how to use a tuple as a function parameter. I 
> tried using a couple different options like `tuple` and 
> `TypeTuple` as well as trying to convert the function into a 
> template, but didn't have any better luck with those. I feel 
> like I'm probably missing something silly, and any help would 
> be appreciated.

Thats being successfully passed, what the compiler hates is that 
tuples could be mixed types

`auto foo(tuple!(int,bool,float) t,int i)=>t[i];` should and does 
fail

You happen to be passing in all strings but thats not what the 
api is for, you could probaly make it compile with an ugly cast, 
verbose switch, but if you know its all the same type you should 
use an array(`foo(T,N)(T[N] arr...)` btw)