[john_b]

Generating random numbers in (0,1) is mathematically different than generating random numbers, even from the same type of distribution, in [0,1), (0,1], or [0,1]. Equating all of these, as the article points out, rarely causes problems in practice, but it is nonetheless a conceptual error.

If you'll pardon me pulling out my soapbox for a moment, this kind of bug would be less common if the "programmers don't need math" attitude was not a successful meme in our culture. The notion of "between zero and one" may seem straghtforward and obvious, but is actually ambiguous. Perhaps, given the number of distinct floating point values that can be represented in the interval (0,1), it would hardly seem to matter what interpretation of "between zero and one" is used. But in mathematics you will never see such terminology used without a qualifying statement that clarifies* the meaning.

*E.g. "between 0 and 1, inclusive", "on the closed interval bounded by 0 and 1", "[0,1]", etc.