Hello, On 2021年1月14日 22:05:37 +1100 Steven D'Aprano <[email protected]> wrote:
> On Wed, Jan 13, 2021 at 08:17:26PM +0300, Paul Sokolovsky wrote: > > > > Besides, we probably don't want to prohibit side-effects in > > > `__bool__`. That would prohibit useful tricks such as putting > > > logging calls into a method you are trying to debug. > > > > Surely, if we do that, we wouldn't use Haskell's definition of > > purity ;-). Rather, a practical definition of purity, > > Python-style. > > It's not *Haskell's* definition, it's pretty much *everyone's* > definition of pure. > > https://en.wikipedia.org/wiki/Pure_function > > > > > For example, print() would be considered "pure", as its purpose is > > to provide program output, not arbitrarily change program state > > > Is writing to an external file a change to program state? Keep in > mind that programs can get state from external files. Please reread the reply about "not having non-local side effects". NotHavingNonLocalSideEffects is a bit longish for an annotation identifier though... > > I would say that what you are describing is not a distinction between > pure and impure functions, You say that as if you propose some better identifier for annotation ;-). I personally would be fine if the annotation is: def print(*Any) -> PythoniclyPure: ... I'm talking about small-scale semantic distinctions required for capture needed large-scale semantic effect. Naming, when it comes to it, will be subject of long, looooooong bikeshedding. (Which already started, thanks!) > based on whether or not they can be safely > optimised away without a change in visible behaviour. The distinction > you are proposing is into two arbitrary sets of functions, some of > which can be optimized away and some which can't, regardless of > whether or not that optimisation leads to change in visible behaviour. > > If you want to argue for that, fine, do so, but don't call impure > functions "pure". [] -- Best regards, Paul mailto:[email protected] _______________________________________________ Python-Dev mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/[email protected]/message/QBWTRDJZHDXYAOY42DZMETRNPOLHPFZH/ Code of Conduct: http://python.org/psf/codeofconduct/