On Wednesday, June 15, 2016 at 8:42:33 AM UTC+5:30, Steven D'Aprano wrote: > On Wed, 15 Jun 2016 01:33 am, Rustom Mody wrote: > > > On Tuesday, June 14, 2016 at 8:13:53 AM UTC+5:30, Steven D'Aprano wrote: > >> No. The sun exploding was me gently mocking you for your comment > >> disputing the "unconditional" part. Yes, you are technically right that > >> technically the "else" block will only run if no "break" is reached, and > >> no "return" is reached, no exception is raised, also that os._exit or > >> os.abort aren't called, the CPU doesn't catch fire, and the world isn't > >> destroyed. > >> > >> If we try to enumerate all the things which could prevent the "else" > >> block from running, we'll be here for decades. But, and this is the point > >> that everyone seems to have missed, * every single one of those things* > >> is completely independent of the for...else statement. > >> > >> *Including* the presence or absence of a "break". > > > > This is real wild: A break that is inside a for is independent of the > > for?!?! > > If that's what I said, you would be right to question me. But that's not > what I said. > > It is legal syntax to have for...else without a break, or a break inside a > for block with no else. And, if you really want to nitpick, you can even > have a break statement without a for. (Just stick it inside a while loop > instead.) > > I know that's it's great fun to pick at nits without making a good faith > effort to communicate, but honestly Rustom, your following comments do > suggest that you understood what I was saying. > > > [...] > > This *desire* for what you call isolation is a standard tenet of > > semantics and is right > > > > It is called compositionality > > > > Inn programming: > > https://en.wikipedia.org/wiki/Denotational_semantics#Compositionality > > > > More general linguistics: > > https://en.wikipedia.org/wiki/Principle_of_compositionality > > Thanks for that. > > > > However gotos break compositionality unless one introduces heavy artillery > > like continuations > > > > And break is a euphemism for goto > > Sort of. A break is a jump, and a goto is a jump, but apart from that, > they're not really the same thing. A goto can jump (almost) anywhere. > Depending on the language, they can jump into the middle of functions, or > into the middle of loops. That's what makes them powerful enough to break > compositionality. But break can only jump to a single place: to the > statement that follows the for...else compound statement. It's more like a > return than a goto.
I thought there'd be many examples for showing that break is just goto in disguise... Evidently not So here is an example in more detail for why/how break=goto: http://blog.languager.org/2016/06/break-is-goto-in-disguise.html [Return/yield are more interesting and complicated...] -- https://mail.python.org/mailman/listinfo/python-list
