On Monday, 8 June 2015 at 16:27:36 UTC, Artur Skawina wrote:
On 06/08/15 17:14, Jeffrey Tsang via Digitalmars-d wrote:
On Sunday, 7 June 2015 at 14:17:45 UTC, Artur Skawina wrote:
On 06/07/15 11:05, Jeffrey Tsang via Digitalmars-d wrote:
I use a mixin template to define exactly one symbol, and at
instantiation I wish to use that symbol immediately, once.
AFAICT you're asking for the commented-out line in
auto Tmpl() = l;
void main(string[] argv) {
auto l = argv.length;
mixin Tmpl!() a;
assert(a.Tmpl==l);
//assert(a==l);
}
to work. That would probably be enough, make sense and have
no serious backward compat issues.
There are three separate things I would like to have:
1. Eponymous trick
mixin T foo(T)() {
return bar;
}
as pure syntactic sugar for
mixin template foo(T) {
T foo() {
return bar;
}
}
This part already works, if you leave out the 'mixin' annotation
(which only prevents non-mixin use). "Normal" templates can be
mixed in too, see my `Tmpl` example above.
T foo(T)() {
return bar;
}
auto f(int bar) {
mixin foo!double blah;
return blah.foo();
}
void main() {
assert (f(42)==42.0);
}
Recursive mixin templates, which is mostly the reason I'm using
this, won't work:
string foo(string x)() {
return x;
}
string foo(string x, T...)() {
mixin foo!T _foo;
return x ~ y ~ _foo.foo();
}
// mixin foo!("a", "b"); // dies on foo not a template
2. Eponymous trick, calling end
mixin foo!T;
to also include as syntactic support
alias foo = foo!T.foo;
as well as the named version you listed.
No, that would hide the `foo` template symbol.
There's no such problem with the named version (other than
the eponymous look-up not working).
I just mean the eponymous look-up part of it, whatever the
compiler-generated alias looks like.
3. Inline/anonymous mixins
Some way of writing the equivalent of
bar = (mixin foo!T)() + 3;
This part I'm not sure about. Can't think of an interesting
use case, that wouldn't be better handled in some other way.
The obvious workaround would be:
bar = { mixin foo!T f; return f()+3; }(); // today:
`f.foo()+3`
[`{...}()` might result in a lambda/closure right now, but that
should really be fixed (ie defined as a special case)]
artur
Yeah, it's probably easier to do
auto foo = { mixin foo!T f; return f.foo; }()
and take one name. With the mixin using enclosing scope, can it
be function and not delegate?
