use list for unique_task2name

[dlashua]

Fixes #99

[craigbarratt]

This looks great. My only suggestion is to use a set instead of list, which is more efficient if we had a lot of names, and also add and discard don't require testing beforehand.

[craigbarratt]

It would be more efficient to use a set, in which case the last two lines can just be a single-line discard (which is a no-op if not present)

[craigbarratt]

This would be set() instead of []

[dlashua]

I considered a set because it makes the values unique automatically. But, having never used one before, when I looked up the differences between a list and set I read that items in a set could not be changed or replaced. So I went with a list because I knew it would work (i.e. I chickened out on having to debug it if it didn't work as I expected).

I'll convert to a set.

[craigbarratt]

set elements have the same restriction as dict keys - they have to be immutable (so their hashed value cannot change). So set elements and dict keys can't be things like lists, sets, dicts, or objects, since they can be changed.

A set is just like a dict where there isn't a value and the set members are the dict keys.

[craigbarratt]

Looks great; fixes #99.

[dlashua]

A set is just like a dict where there isn't a value and the set members are the dict keys.

well... TIL about object hashes in python. I've never tried to use a dict as a dict key before, but now I know why I can't. Thanks!