improving the join function

[Philippe Sigaud]

On Tue, Oct 12, 2010 at 02:33, Andrei Alexandrescu
<SeeWebsiteForEmail at erdani.org> wrote:

> ElementType!R1[] join(R1, R2)(R1 items, R2 sep)
> if (isInputRange!R1 && isForwardRange!R2
>    && is(ElementType!R2 : ElementType!R1);

> Notice how the separator must be a forward range because it gets spanned
> multiple times, whereas the items need only be an input range as they are
> spanned once. This is at the same time a very general and very precise
> interface.

I like this and I've nothing against this signature, but I'm probably
biased. When I look at this, I don't even look for the function name:
the constraints (ie, the interface) is what catches my eye.



> One thing is still bothering me: the array output type. Why would the
> "default" output range be an array? What can be done to make join() at the
> same time a general function and also one that works for strings the way the
> old join did? For example, if I want to join things into an already-existing
> buffer, or if I want to write them straight to a file, there's no way to do
> so without having an array allocation in the loop. I have a couple of ideas
> but I wouldn't want to bias yours.

Let to my own, I'd make that a lazy Join struct range: an input range
that delivers R1 elements one by one, interspersed with R2 elements.
Hmm, now that I think a bit more, I was taking them both (or at least
R1) to be ranges of ranges:  join(["the","quick","red","fox"], " ").
Man, it's 4 pm now, I'll stop.