Re: Can this recursive template type with named type parameters be simplified or improved?

[Hakan Aras via Digitalmars-d-learn]

On Sunday, 21 October 2018 at 21:23:35 UTC, aliak wrote:
Hi, I'm playing around with a recursive template type that 
allows for named template parameters. The problem is that it 
requires a lot of repetition and becomes more error prone as 
the number of named arguments increase. So


1) Any ideas on how to make it less error prone? less 
repetition? a better way to do this?
2) Right now I can only have named optional parameters. Any 
ideas on how to make named required parameters (e.g. the first 
type parameter of Type).




I don't know if this is at all helpful, but I spent an hour on 
it, so I'm going to share it:


https://pastebin.com/cGZwc649

You can wrap it in a template if you want to retain the ability 
to pass arguments without names.


Regards,
Hakan

Can this recursive template type with named type parameters be simplified or improved?

[aliak via Digitalmars-d-learn]

Hi, I'm playing around with a recursive template type that allows 
for named template parameters. The problem is that it requires a 
lot of repetition and becomes more error prone as the number of 
named arguments increase. So


1) Any ideas on how to make it less error prone? less repetition? 
a better way to do this?
2) Right now I can only have named optional parameters. Any ideas 
on how to make named required parameters (e.g. the first type 
parameter of Type).


Here's an example of a type that has one required parameter and 4 
optional named parameters:


private struct TypeImpl(
T,
string _arg0 = null,
int _arg1 = 0,
float _arg2 = 0,
alias _arg3 = null,
) {
alias Arg0 = _arg0;
alias Arg1 = _arg1;
alias Arg2 = _arg2;
alias Arg3 = _arg3;
public alias arg0(string value) = TypeImpl!(T, value, Arg1, 
Arg2, Arg3);
public alias arg1(int value) = TypeImpl!(T, Arg0, value, 
Arg2, Arg3);
public alias arg2(float value) = TypeImpl!(T, Arg0, Arg1, 
value, Arg3);

public static template arg3(alias value) {
alias arg3 = TypeImpl!(T, Arg0, Arg1, Arg2, value);
}
}

public template Type(T) {
alias Type = TypeImpl!(T);
}

void main() {
void fun() {}
alias U = Type!int
.arg0!"string"
.arg1!3
.arg3!fun;
pragma(msg, U);
}

Cheers,
- Ali