Use namedtuple for interval

[hyanwong]

Fixes #784

[benjeffery]

So this doesn't break anything as the namedtuple supports indexing right? We'd need tests for the new left and right attributes though. Is there much of a perf hit?

[hyanwong]

So this doesn't break anything as the namedtuple supports indexing right?

Yes

We'd need tests for the new left and right attributes though.

I've changed e.g. seek to use .right, and (I think) nexus uses both .left and .right, so I think the coverage stats will remain the same.

Is there much of a perf hit?

I would hope it would be negligible. But a browse around the internet implies accessing via name is a tad slower (damn), so we could switch to [0] and [1] within code that needs to be fast, I guess. I think the names are a big advantage, though, so this is still worth doing.

[jeromekelleher]

I don't we need to worry about the perf hit if there is one, it's not going to matter.

We do want to explicitly test that we keep the old behaviour, though, and what the new behaviour is.

I don't think we should merge this until after 0.3.0, unless there's a good reason. We don't want to diverge to much from the betas and only put vital bugfixes in at this point.

[benjeffery]

Yep, agreed on the merge freeze and explicit tests. Otherwise this is good.

[hyanwong]

Explicit test added. Ready to merge after 0.3.0 released.

[jeromekelleher]

OK, tagged this with the 0.3.1 milestone so we know when to merge it.

[hyanwong]

It might be nice (although certainly not vital) to add a .span property too:

BaseInterval = collections.namedtuple("BaseInterval", ["left", "right"])
class Interval(BaseInterval):
    @property
    def span(self):
        return self.right-self.left

Overkill?

[jeromekelleher]

I don't see any harm, once it doesn't clash with the namedtuple behaviour.

[benjeffery]

Great, thanks for the extra tests. Happy to have span later as a separate PR.