On Friday, 17 November 2017 at 01:16:38 UTC, H. S. Teoh wrote:
It should be .empty, .popFront, and .front, not .pop.
Also, these methods are *range* primitives, and over time, we
have come to a consensus that generally speaking, it's a bad
idea to conflate containers with ranges over containers. The
main thing is that iterating over a range is supposed to
consume it, which is usually not what you want with a container.
The usual idiom is to separate the two concepts, and have the
container provide a mechanism for returning a range over its
contents, usually via .opIndex with no arguments, or .opSlice.
Then you would just write:
foreach (e; myContainer[]) { // [] calls .opIndex/.opSlice
...
}
Unfortunately, built-in arrays, which are also ranges, are one
exception to this rule that, due to their ubiquity in D, also
serve to mislead newcomers to D about when/where range
primitives should be implemented. Generally speaking, built-in
arrays should not be considered exemplary in this respect, but
rather should be understood as exceptions. The general
convention is to separate your containers from ranges over its
contents, and to provide .opIndex / .opSlice that constructs a
range over the container when needed.
The other consideration is that if you don't really need range
functionality, i.e., the only thing you want to do with your
container is to put it in a foreach loop, then you can sidestep
this whole mess and just implement .opApply for your container
and call it a day. Of course, then you won't be able to use
generic algorithms like those in std.algorithm with your
container, but if you didn't intend to anyway, it's not a big
deal.
T
Thanks T! Good information, especially "iterating over a range is
supposed to consume it". I have been reading
dlang.org->Documentation->Language Reference, but should have
also read dlang.org->Dlang-Tour->Ranges. Although that page makes
a distinction about "range consumption" with regard to a
"reference type" or a "value type" and it isn't clear to me why
there would be a difference.
