We are currently like a dozen of people talking about multiple sections of a single subject.
Isn't it easier to talk on a forum? *Am I the only one* who thinks mailing list isn't easy when lots of people talking about multiple subjects? Of course we would put the link in the mailing list so that everyone can join. A forum (or just few "issues" thread on github) is where we could have different thread in parallel, in my messages I end up with like *10 comments not all related*, in a forum we could talk about everything and it would still be organized by subjects. Also, it's more interactive than email on a global list, people can talk to each other in parallel, if I want to answer about a mail that was 10 mail ago, it gets quickly messy. We could all discuss on a gist or some "Issues" thread on GitHub. 2018-02-28 22:38 GMT+01:00 Robert Vanden Eynde <robertv...@gmail.com>: > Le 28 févr. 2018 11:43, "Chris Angelico" <ros...@gmail.com> a écrit : > > > It's still right-to-left, which is as bad as middle-outward once you > > combine it with normal left-to-right evaluation. Python has very > > little of this [..] > > I agree [....] > > >> 2) talking about the implementation of thektulu in the "where =" part. > > > ? > > In the Alternate Syntax, I was talking about adding a link to the thektulu > (branch where-expr) > <https://github.com/thektulu/cpython/commits/where-expr> > implementation as a basis of proof of concept (as you did with the other > syntax). > > >> 3) "C problem that an equals sign in an expression can now create a > name inding, rather than performing a comparison." > > As you agreed, with the "ch with ch = getch()" syntax we won't > accidentally switch a "==" for a "=". > > I agree this syntax : > > ``` > while (ch with ch = getch()): > ... > ``` > > doesn't read very well, but in the same way as in C or Java while(ch = > getch()){} or worse ((ch = getch()) != null) syntax. > Your syntax "while (getch() as ch):" may have a less words, but is still > not clearer. > > As we spoke on Github, having this syntax in a while is only useful if the > variable does leak. > > >> 5) Any expression vs "post for" only > > > I don't know what the benefit is here, but sure. As long as the > > grammar is unambiguous, I don't see any particular reason to reject > > this. > > I would like to see a discussion of pros and cons, some might think like > me or disagree, that's a strong langage question. > > > 6) with your syntax, how does the simple case work (y+2 with y = x+1) ? > > What simple case? The case where you only use the variable once? I'd > write it like this: > > (x + 1) + 2 > > >> The issue is not only about reusing variable. > > > If you aren't using the variable multiple times, there's no point > > giving it a name. Unless I'm missing something here? > > Yes, variables are not there "just because we reuse them", but also to > include temporary variables to better understand the code. > Same for functions, you could inline functions when used only once, but > you introduce them for clarity no ? > > ``` > a = v ** 2 / R # the acceleration in a circular motion > f = m * a # law of Newton > ``` > > could be written as > > ``` > f = m * (v ** 2 / R) # compute the force, trivial > ``` > > But having temporary variables help a lot to understand the code, > otherwise why would we create temporary variables ? > I can give you an example where you do a process and each time the > variable is used only one. > > >> 8) > >> (lambda y: [y, y])(x+1) > >> Vs > >> (lambda y: [y, y])(y=x+1) > > Ewww. Remind me what the benefit is of writing the variable name that > many times? "Explicit" doesn't mean "utterly verbose". > > Yep it's verbose, lambdas are verbose, that's why we created this PEP > isn't it :) > > > 10) Chaining, in the case of the "with =", in thektulu, parenthesis were > > mandatory: > > > > print((z+3 with z = y+2) with y = x+2) > > > > What happens when the parenthesis are dropped ? > > > > print(z+3 with y = x+2 with z = y+2) > > > > Vs > > > > print(z+3 with y = x+2 with z = y+2) > > > > I prefer the first one be cause it's in the same order as the "post for" > > > > [z + 3 for y in [ x+2 ] for z in [ y+2 ]] > > > With my proposal, the parens are simply mandatory. Extending this to > > make them optional can come later. > > Indeed, but that's still questions that can be asked. > > >> 11) Scoping, in the case of the "with =" syntax, I think the parenthesis > >> introduce a scope : > >> > >> print(y + (y+1 where y = 2)) > >> > >> Would raise a SyntaxError, it's probably better for the variable beeing > >> local and not in the current function (that would be a mess). > >> > >> Remember that in list comp, the variable is not leaked : > >> > >> x = 5 > >> stuff = [y+2 for y in [x+1] > >> print(y) # SyntaxError > > > Scoping is a fundamental part of both my proposal and the others I've > > seen here. (BTW, that would be a NameError, not a SyntaxError; it's > > perfectly legal to ask for the name 'y', it just hasn't been given any > > value.) By my definition, the variable is locked to the statement that > > created it, even if that's a compound statement. By the definition of > > a "(expr given var = expr)" proposal, it would be locked to that > > single expression. > > Confer the discussion on scoping on github (https://github.com/python/ > peps/commit/2b4ca20963a24cf5faac054226857ea9705471e5) : > > """ > In the current implementation it looks like it is like a regular > assignment (function local then). > > Therefore in the expression usage, the usefulness would be debatable (just > assign before). > > But in a list comprehension *after the for* (as I mentioned in my mail), > aka. when used as a replacement for for y in [ x + 1 ] this would make > sense. > > But I think that it would be much better to have a local scope, in the > parenthesis. So that print(y+2 where y = x + 1) wouldn't leak y. And when > there are no parenthesis like in a = y+2 where y = x+1, it would imply > one, giving the same effect as a = (y+2 where y = x+1). Moreover, it > would naturally shadow variables in the outermost scope. > > This would imply while data where data = sock.read(): does not leak data > but as a comparison with C and Java, the syntax while((data = sock.read()) > != null) is really really ugly and confusing. > """ >
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