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Shouldn't this be array instead of matrix? And why skip the doctest?

This same issue come up multiple times below.

Doctest has an existing flaw/feature, in that it doesn't do float comparisons. Down below, it's just string compare.
When system precision affects the result, small tolerances can lead to test failure.
I'll have a hard look at it again, because it annoys me no end.
(Might even have to submit a patch to the Doctest project ;-)

All the round() and other tricks to get around it are just confusing for users who look at the examples.