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On Monday, 20 September 2021 at 18:08:03 UTC, Alexandru Ermicioi wrote:
>On Monday, 20 September 2021 at 13:24:50 UTC, Elmar wrote:
>Providing default implementation support seems not more difficult:
mixin Interface!("MyInterface",
q{
static immutable PI = 3.141592f;
default static immutable CONSTANT = 0.0f;
float toImplement(string s);
default float isDefaulted()
{
return (CONSTANT ^^ PI) % toImplement(r"tau"));
}
});
Providing default method implementations without code duplication and too much verbosity could work by defining the default method implementations as compile-time token strings. The above would generate
You can actually try use mixin templates, not just mixin strings. See https://dlang.org/spec/template-mixin.html .
It has nicer syntax although not as powerful as mixin strings. You can also mix in the template into a dedicated scope inside implementor of interface:
mixin MyDefaultImpl!() myScope;
Yeah, using mixin templates is exactly the point of the code snippet you have quoted, but together with string mixins it allows one to mimic syntax features. I do collect some language features I'd like to see in D and if I ever should have enough time, I'd prototype them with string mixins for others to try them.
I didn't try it, but you may be able to mimic default methods using this feature, in conjunction with alias this expression, although I'm pretty skeptic about this due to mangled name generation (i.e haven't tried it).
So in your class you may try and explore whether this works:
mixin MyDefaultImpl!() def;
alias this def;
I've been using alias this in mixin templates recently. According to Online D Editor, it works.