A recent pull request discussion got me thinking: The ability to
"downgrade" a range to a less featureful one -- wrapping a random
access range in an input range, say -- can be very useful
sometimes, particularly for testing. The pull request in
question was Walter's LZ77 module, where he has added an input
range type solely for the purpose of ensuring that all code paths
are exercised in unittests. Coincidentally, I currently find
myself in need of the exact same functionality for a piece of
range code I'm working on.
I think this would be a generally useful thing, enough so to
warrant its inclusion in std.range. It's also rather trivial to
implement. The question is, what is a good API? I'm thinking a
single type which can be instantiated differently based on
template parameters. It is important that the range never
aliases itself away to the wrapped type, as that would somewhat
defeat its purpose.
Example:
enum RangeFeatures
{
input,
forward,
randomAccess,
...
}
struct RestrictedRange(Range, RangeFeatures features)
{
private Range m_range;
static if (features == RangeFeatures.input)
{
auto front() @property { return m_range.front() }
}
}
