Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On Sun, Mar 4, 2018 at 11:04 PM, Chris Angelico wrote: > On Mon, Mar 5, 2018 at 2:49 PM, Mike Miller > wrote: > > Yes, thanks: > > > > [ f(y), g(y) for x, h(x) as y in things ] > > > > > > Dyslexics untie! > > :) > > Hmm. The trouble here is that

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On Mon, Mar 5, 2018 at 2:49 PM, Mike Miller wrote: > Yes, thanks: > > [ f(y), g(y) for x, h(x) as y in things ] > > > Dyslexics untie! :) Hmm. The trouble here is that a 'for' loop is basically doing assignment. When you say "for x, h(x) as y in things", what

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Yes, thanks: [ f(y), g(y) for x, h(x) as y in things ] Dyslexics untie! On 2018-03-04 19:45, Chris Angelico wrote: ___ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct:

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On Mon, Mar 5, 2018 at 2:39 PM, Mike Miller wrote: > > On 2018-03-03 16:51, Greg Ewing wrote: >>> >>> 2018-03-03 8:40 GMT+01:00 Nick Coghlan : pairs = [(f(y), g(y)) for x in things with bind(h(x)) as y] >> >> >> I don't mucn like "with

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On 2018-03-03 16:51, Greg Ewing wrote: 2018-03-03 8:40 GMT+01:00 Nick Coghlan :    pairs = [(f(y), g(y)) for x in things with bind(h(x)) as y] I don't mucn like "with bind(h(x)) as y" because it's kind of like an abstraction inversion -- you're building something

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

> I know Guido is on record as not wanting to allow both "for name in > sequence" and "for name = expr" due to that being a very subtle distinction > between iteration and simple assignment (especially given that Julia uses > them as alternate spellings for the same thing), but I'm wondering if it

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

> What the heck, if it was good enough for PL/1... It would still be parsable indeed. A keyword available in a context would then be something new in the language. > Choice of syntax is important, though. It's all very well > to come up with an "insert syntax here" proposal that has > some big

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

> Robert Vanden Eynde wrote: >> >> But I think that the implementation of print(y with y = x + 1) would >> be more close to next(y for y in [ x+1 ]) > > > WHy on earth should it be? Expanding that gives you a generator > containing a loop that only executes once that is immediately run > to yield

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Nick Coghlan writes: > pairs = [(f(y), g(y)) for x in things with y = h(x)] > contents = [f.read() for fname in filenames with open(fname) as f] This is horrible. I think Julia is just weird: in normal English we do distinguish between equality and membership. "x in y" is a very

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Soni L. writes: > [(lambda y: (f(y), g(y)))(h(x)) for x in things] ? MicroLisp? ___ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Robert Vanden Eynde wrote: The "make it a keyword in a context" might lead to things like "print(where where where = where)", not sure you'd want that :) What the heck, if it was good enough for PL/1... But that's just a choice of syntax, Choice of syntax is important, though. It's all

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

2018-03-03 8:40 GMT+01:00 Nick Coghlan : pairs = [(f(y), g(y)) for x in things with bind(h(x)) as y] I don't mucn like "with bind(h(x)) as y" because it's kind of like an abstraction inversion -- you're building something complicated on top of something complicated in

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Robert Vanden Eynde wrote: But I think that the implementation of print(y with y = x + 1) would be more close to next(y for y in [ x+1 ]) WHy on earth should it be? Expanding that gives you a generator containing a loop that only executes once that is immediately run to yield exactly one

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Nathan Goldbaum wrote: Where is also very common in numpy. So if someone did: from numpy import * data = where(condition) They might have issues Bummer, I didn't know numpy used it. That puts rather a big dampener on the idea of making it a keyword. :-( Remaining options include: * Make

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Robert Vanden Eynde wrote: One could see : print(y with y = x+1) As a shortcut for : print(next(y for y in [ x+1 ])) Or more straightforwardly, print((lambda y: y)(x + 1)) This is how the semantics of let-type constructs is often defined in lambda-calculus-inspired languages such as

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On Sat, Mar 3, 2018 at 5:12 AM Oleg Broytman wrote: > On Sat, Mar 03, 2018 at 02:36:39PM +1300, Greg Ewing < > greg.ew...@canterbury.ac.nz> wrote: > >[(f(y), g(y)) for x in things where y = h(x)] > > > > Possible objections to this: > > > > * Requires a new keyword, which

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

Le 3 mars 2018 08:45, "Nick Coghlan" a écrit : On 3 March 2018 at 11:36, Greg Ewing wrote: > 1. Name bindings local to an expression: > >roots = ([(-b-r)/(2*a), (-b+r)/(2*a)] where r = sqrt(b*b-4*a*c)) > > B. In an expression, surrounded by

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On 2018-03-03 08:09 AM, Oleg Broytman wrote: On Sat, Mar 03, 2018 at 02:36:39PM +1300, Greg Ewing wrote: [(f(y), g(y)) for x in things where y = h(x)] Possible objections to this: * Requires a new keyword, which may break existing code. - Yes, but "where"

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On 3 March 2018 at 07:45, Nick Coghlan wrote: > On 3 March 2018 at 11:36, Greg Ewing wrote: >> >> 1. Name bindings local to an expression: >> >>roots = ([(-b-r)/(2*a), (-b+r)/(2*a)] where r = sqrt(b*b-4*a*c)) >> >> B. In an expression,

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On 3 March 2018 at 11:36, Greg Ewing wrote: > 1. Name bindings local to an expression: > >roots = ([(-b-r)/(2*a), (-b+r)/(2*a)] where r = sqrt(b*b-4*a*c)) > > B. In an expression, surrounded by parentheses for > disambiguation. Bindings are visible only within

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

On 3 March 2018 at 11:36, Greg Ewing wrote: > PEP 572 as it stands seems to have many problems: > > * Asymmetry between the first and subsequent > uses of the bound value > * Embedded as-clauses are subtle and hard to spot > * Ever more convoluted semantics are

Re: [Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

The syntax you propose is already in the Alternate syntax and there is an implementation at https://github.com/thektulu/cpython/tree/where-expr Already discussed, but no conclusion, for me I see two different proposals, the "[y for x in range(5) with y = x+1]" in comprehensions list, and the case

[Python-ideas] An alternative to PEP 572's Statement-Local Name Bindings

PEP 572 as it stands seems to have many problems: * Asymmetry between the first and subsequent uses of the bound value * Embedded as-clauses are subtle and hard to spot * Ever more convoluted semantics are being invented to address percieved pitfalls Alternative proposal