Steve, I've seen *unless* discussed and rejected before, but it is a good enough syntax for the purpose of asserting invariants, and it should be useful for other purposes (because it has been proposed before).
The semantics are clear, and the implementation is simple with the new Python parser shortcutting to an "*if not"*. I do really like this option. On Sun, Sep 12, 2021 at 1:46 AM Steven D'Aprano <[email protected]> wrote: > On Sat, Sep 11, 2021 at 02:30:10PM -0400, Juancarlo Añez wrote: > > > *invariant* cond: etc > > A software invariant is still an assertion. > > In another post, I semi-suggested a new (soft) keyword: > > unless condition: > # block > raise Exception > > But really, it's just an "if not". > > if not condition: > unless condition: > assert condition: > > are all exactly the same amount of typing. It's not clear that learning > a new keyword `unless` is more readable than just using `if not`. > > I think it might work better in languages that attempt to follow natural > language (e.g. XTalk languages) than one like Python with a relatively > minimal amount of syntax. But it is clear to me that using `assert` for > non-assertions is misleading. > > -- > Steve > _______________________________________________ > Python-ideas mailing list -- [email protected] > To unsubscribe send an email to [email protected] > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/[email protected]/message/ERBJUTXNAVALGUGDPC7EHQT3LUP3NQHB/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- Juancarlo *Añez*
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