Generality creep

[H. S. Teoh]

On Thu, Mar 28, 2019 at 01:04:58PM -0400, Andrei Alexandrescu via Digitalmars-d wrote:
[...]
> Part of that is we've been cagey about defining copy and assignment
> semantics of ranges in a simple and comprehensive manner. It seems to
> me going with these is the right thing:
> 
> * Input ranges are copyable and assignable, and have pointer semantics
> (all copies refer to the same underlying position, and advancing one
> advances all others).
> 
> * Forward ranges are copyable and assignable, but distinct copies
> refer to distinct positions in the range such that advancing one does
> not advance the others.
> 
> * We don't support other semantics.

What about classes that wrap ranges? E.g., std.ranges.interfaces.  Since
classes are reference types, this would mean it's impossible to use
those interfaces with forward ranges or above, which is a show-stopping
limitation (e.g., if you need to return two different range types
selected at runtime -- the current solution is to wrap them in the
appropriate class using std.ranges.interfaces).


T

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