On Friday, 20 November 2015 at 18:23:57 UTC, HaraldZealot wrote:
All ranges in Phobos pass by value, but if I have output range
with state like cumulative statistics this is useless.
After discussion with Dicebot I try this work-arround:
http://dpaste.dzfl.pl/8af8eb8d0007
It is unfinished. But direction is observable.
Is this good solution? And how about to include something like
this tool in Phobos?
I'm not sure how useful this is as opposed to plain pointers. For
structs, since `foo.bar` is the same as `(&foo).bar`, you may as
well use a pointer, and the only thing it saves for numbers is a
pointer deference or two.
You say ranges are pass-by-value, but that's not entirely true.
Ranges themselves can be classes, or be made references via
std.range.refRange. Range elements can be made lvalues by using
ref functions [1].
As for the code:
* Your example usage (x = x += x = (x * 5)) is confusing, due to
the chained assignments.
* I wouldn't mark this struct as @safe because the passed value
may leave scope, causing invalid dereferences.
* There's no point in making the Reference struct a template, as
the function its defined in is also a template. Just replace
usages of U with T.
[1]: http://dlang.org/function.html#ref-functions see also
std.range.interface.hasLvalueElements
