output ranges: by ref or by value?

[Michel Fortin]

On 2010-01-02 09:59:51 -0500, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> That's an idea, and names are powerful, but I think it's reasonable to 
> not expect miracles from that name change. It has disadvantages too - 
> "input range" vs. "forward range"  clarifies there's a conceptual 
> relationship between the two, whereas "streams" are different from 
> anything else.

I'm not expecting a miracle from it either, it'd just be much less confusing.

You could say that assignment of an input stream might or might not 
save its state (depending on the stream type) so you must call save() 
to save the state when working with streams, but ranges are guarantied 
to save their state on assignment, thus behaving more predictably and 
just like arrays. So if you're working only with ranges, not streams, 
you never need to worry about save().

A similar option would be to have both input ranges and input streams:

* input range:  by value semantics, no need for save()
* input stream: by reference semantics

A pointer to an input range would thus automatically qualify as an 
input stream, so it's easy to give an input range to a function taking 
an input stream. Well, except for stack-allocated ranges in SafeD for 
which you can't create a pointer. This pretty much break the idea, I 
think.


-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/