On Monday, 22 April 2024 at 11:36:43 UTC, Chloé wrote:
I wish to adapt this interface to a forward range for use with
foreach and Phobos' range utilities. This amounts to
implementing empty, front, and popFront, in terms of next and
some state. But there is a choice to be made regarding the
first call to next.
Just to offer an alternative solution (since it sometimes gets
overlooked), there is also the `opApply` approach. You don't get
full forward range status, and checking whether it's empty
essentially requires doing something like std.algorithm
`walkLength`, but if all you need is basic iteration, it can be a
simpler solution:
```d
struct Range {
private I iter;
this(I iter) { this.iter = iter; }
int opApply(scope int delegate(T* t) dg) {
while (auto current = next(iter)) {
if (auto r = dg(current))
return r;
}
return 0;
}
}
void main() {
I someIter; // = ...
auto range = Range(someIter);
foreach (const t; range) {
writeln(*t);
}
}
```
