On Tuesday, 28 May 2019 at 13:43:45 UTC, Nick Treleaven wrote:
Hi,
Last week's TWiD had a tip that didn't make sense:
http://dpldocs.info/this-week-in-d/Blog.Posted_2019_05_20.html#tip-of-the-week
template Locals(int i) {
alias Whatever = int;
}
static foreach(i; [1, 2, 3]) {
Locals!i.Whatever;
}
The body is just `int;`. Not sure how to reach Adam. What was
intended?
Yes, intended, but also incomplete. The idea there is to use the
template as a namespace for whatever local stuff you had. (I
adapted this from a reflection thing where Whatever would have
been an alias to a member type, and then in simplifying to get to
just the new idea - and in a rush to type it up that day - I
removed like all the context).
So it might actually be more like (still an incomplete example
but more complete):
void test(T)() {
template Locals(int i) {
static if(is(typeof(__traits(getMember, T,
__traits(allMembers, T)[i])) Ret == return))
alias ReturnValue = Ret;
}
static foreach(idx, t; __traits(allMembers, T)) {
mixin("auto " ~ t ~ "() { return
Locals!idx.ReturnValue.init; }");
}
}
So now the Locals template wraps a bunch of aliases so we can
refer to them more succinctly later.
A regular alias defined inside that static foreach would end up
being duplicated in future iterations. Putting the extra {}
around it would mean the mixed in function would not be visible
outside.
so the Locals template is just a collection of convenience
aliases in a namespace.
