Thread overview
spec: template instantiations
November 20
I don't under this:

https://dlang.org/spec/template.html#instantiation_scope

The text seems to contradict the example.

If a template declares multiple entities then is it possible to instantiate all of them at one or is each entity instantiated separately?

Suppose we have:

template Transformer(From, To) // From and To are types, too
{
    To transform(From from)
    {
        import std.conv;
        return to!(To)(from);
    }

    class Modificator
    {
        From f;
        To t;
        this(From f) { /*...*/ }
    }
}

Then is there way to instantiate both 'transform' and 'Modificator' at once?



November 20
On Friday, 20 November 2020 at 20:59:56 UTC, Dibyendu Majumdar wrote:
> I don't under this:
>
> https://dlang.org/spec/template.html#instantiation_scope
>
> The text seems to contradict the example.
>

Please ignore - my mistake.

November 21
On Friday, 20 November 2020 at 20:59:56 UTC, Dibyendu Majumdar wrote:
>
> If a template declares multiple entities then is it possible to instantiate all of them at one or is each entity instantiated separately?
>
> Suppose we have:
>
> template Transformer(From, To) // From and To are types, too
> {
>     To transform(From from)
>     {
>         import std.conv;
>         return to!(To)(from);
>     }
>
>     class Modificator
>     {
>         From f;
>         To t;
>         this(From f) { /*...*/ }
>     }
> }
>
> Then is there way to instantiate both 'transform' and 'Modificator' at once?

I suppose answer is no? So when instantiating, it is always a particular member of the template that is instantiated?
November 21
On Saturday, 21 November 2020 at 00:24:43 UTC, Dibyendu Majumdar wrote:
> On Friday, 20 November 2020 at 20:59:56 UTC, Dibyendu Majumdar wrote:
>>
>> Suppose we have:
>>
>> template Transformer(From, To) // From and To are types, too
>> {
>>     To transform(From from)
>>     {
>>         import std.conv;
>>         return to!(To)(from);
>>     }
>>
>>     class Modificator
>>     {
>>         From f;
>>         To t;
>>         this(From f) { /*...*/ }
>>     }
>> }
>>
>> Then is there way to instantiate both 'transform' and 'Modificator' at once?
>
> I suppose answer is no? So when instantiating, it is always a particular member of the template that is instantiated?

Quite the opposite. When you instantiate a template, the entire template body is instantiated at the same time. You can then access individual members using the `.` operator. So for example:

alias Instance = Transformer!(int, string);
Instance.Modificator m = new Instance.Modificator(123);
string s = Instance.transform(123);