Caching in computing ranges

[Andrei Alexandrescu]

On 10/9/10 18:20 CDT, dsimcha wrote:
> Vote++.  When I added bidirectional support for map(), I felt like any solution
> for doing bidirectional caching was going to suck.  I considered just eliminating
> it, but left it because at the time I was more interested in just getting
> bidirectional/random access working than worrying about the cache issue.  IMHO the
> only range that should be cached is a Cached higher order range.

Cached will be quite a story in and of itself. I can tell you for sure 
we need two related abstractions in std.range:

1. Lookback!Range provides a history that allows the range to look back 
up to n items:

auto r = lookback(file.byLine(), 20);
...
r.lookback(3); // three lines before the current

2. Lookahead!Range similarly allows looking ahead:

auto r = lookahead(file.byLine(), 20);
...
r.lookahead(3); // three lines after the current


Andrei