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Groups > comp.lang.python > #109615
| From | Jussi Piitulainen <jussi.piitulainen@helsinki.fi> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: I'm wrong or Will we fix the ducks limp? |
| Date | 2016-06-07 11:41 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <lf5fusppf14.fsf@ling.helsinki.fi> (permalink) |
| References | (13 earlier) <1465247581.1161240.629720825.10FE129E@webmail.messagingengine.com> <mailman.48.1465247584.2306.python-list@python.org> <87shwq56s8.fsf@elektro.pacujo.net> <drn9tlFnt0qU1@mid.individual.net> <8760tlmny0.fsf@elektro.pacujo.net> |
Marko Rauhamaa <marko@pacujo.net> writes:
> Gregory Ewing <greg.ewing@canterbury.ac.nz>:
>
>> Marko Rauhamaa wrote:
>>> Seriously, though, it is notable that the high-level programming
>>> languages pretty unanimously refuse to make variables first-class
>>> objects. I wonder why.
>>
>> That's an interesting question. One reason might be
>> that in the absence of static type analysis, assigning
>> to a variable holding a reference to another variable
>> would be ambiguous. For example, suppose Python had
>> an & operator that gives you an object referring to
>> a variable somehow. Then, after
>>
>> a = 42
>> b = 17
>> c = &a
>> c = &b
>>
>> does 'c' now hold a reference to the variable 'b', or
>> does it still hold a reference to 'a' and 'a' now
>> holds a reference to 'b'?
>
> If variables were ordinary mutable objects, you'd need a syntax of
> dereferencing, just like in C. Variable objects would be highly
> analogous to single-element arrays, little boxes if you will.
I've had this little piece lying around ever since there last was a
discussion about assignments as expressions. It abuses the ** operator
to store values in boxes; the value of 'expression ** x' is the value of
'expression', with the side effect that afterwards the value of x.it
(the dereferencing!) is also whatever the value of 'expression' was.
class Box(object):
'''Read ** as as and x.it as whatever was saved as x.'''
def __init__(self, init = None):
self.it = init
def __rpow__(self, it): # f() ** self
self.it = it
return self.it
data = iter('piäsiäntösesti ee näen')
from string import ascii_letters as ascii
x, y = Box(), Box()
while (next(data) ** x in ascii and
next(data) ** y in ascii):
print(x.it, y.it)
# Prints one line: p i
There's a further test case in that file, saving the regex match object
during the expression that tests whether there was a match object. Not
entirely satisfactory, but perhaps mildly interesting.
import re
beg = re.compile(r'start=(\w+)')
end = re.compile(r'finis=(\w+)')
b, e = Box(), Box()
for k, line in enumerate(('xxx',
'# start=eka rivi',
'ween',
'ween',
'# finis=vika rivi',
'xxx')):
if not b.it and beg.search(line) ** b:
print(k, b.it.group(1))
elif b.it and end.search(line) ** e:
print(k, e.it.group(1))
break
elif b.it:
print(k, line)
# Prints four lines:
# 1 eka
# 2 ween
# 3 ween
# 4 vika
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I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 07:20 -0700
Re: I'm wrong or Will we fix the ducks limp? Paul Rudin <paul.nospam@rudin.co.uk> - 2016-06-03 15:34 +0100
Re: I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 08:04 -0700
Re: I'm wrong or Will we fix the ducks limp? Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-03 09:35 -0600
Re: I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 08:50 -0700
Re: I'm wrong or Will we fix the ducks limp? Michael Selik <michael.selik@gmail.com> - 2016-06-03 16:04 +0000
Re: I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 16:06 -0700
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-04 12:31 +1000
Re: I'm wrong or Will we fix the ducks limp? Christopher Reimer <christopher_reimer@icloud.com> - 2016-06-03 19:50 -0700
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-04 19:12 +1000
Re: I'm wrong or Will we fix the ducks limp? Matt Wheeler <m@funkyhat.org> - 2016-06-03 15:54 +0000
Re: I'm wrong or Will we fix the ducks limp? Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-04 20:17 -0700
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-05 16:37 +1000
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-05 11:01 +0300
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-05 13:53 -0400
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-05 22:20 +0300
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-05 17:16 -0400
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 11:13 +0300
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-06 13:08 +1200
Re: I'm wrong or Will we fix the ducks limp? Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-05 18:28 -0700
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-05 13:42 -0400
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-05 22:38 +0300
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-06 13:52 +1000
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-06 00:08 -0400
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-07 01:42 +1000
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 17:42 +1200
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-07 20:18 +1000
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-07 14:32 +0200
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-08 02:03 +1000
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-08 10:08 +0200
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-07 11:33 -0400
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-08 09:53 +0200
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-08 18:47 +1000
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-08 11:41 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-08 11:33 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-08 13:01 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-08 13:34 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-08 16:18 +0200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-08 19:37 +0300
Re: I'm wrong or Will we fix the ducks limp? Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-08 19:49 -0700
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 09:30 +0200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 12:19 +0300
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 12:19 +0200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 16:13 +0300
Re: I'm wrong or Will we fix the ducks limp? lists@juliensalort.org (Julien Salort) - 2016-06-09 13:46 +0200
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 14:35 +0200
Re: I'm wrong or Will we fix the ducks limp? Paul Rudin <paul.nospam@rudin.co.uk> - 2016-06-09 11:00 +0100
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 15:56 +0300
Re: I'm wrong or Will we fix the ducks limp? Paul Rudin <paul.nospam@rudin.co.uk> - 2016-06-09 15:09 +0100
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 18:14 +0300
Re: I'm wrong or Will we fix the ducks limp? Paul Rudin <paul.nospam@rudin.co.uk> - 2016-06-09 17:22 +0100
Re: I'm wrong or Will we fix the ducks limp? Paul Rudin <paul.nospam@rudin.co.uk> - 2016-06-09 17:48 +0100
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 22:35 +0300
Re: I'm wrong or Will we fix the ducks limp? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-10 08:31 +0300
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-09 14:36 -0400
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-08 18:29 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 09:50 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 10:10 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 11:55 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 11:48 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 13:08 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 13:25 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 14:48 +0200
Re: I'm wrong or Will we fix the ducks limp? Rustom Mody <rustompmody@gmail.com> - 2016-06-08 05:36 -0700
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-09 17:36 +1000
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 11:46 +0200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-09 13:03 +0300
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 11:42 +0100
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 11:53 +0100
Re: I'm wrong or Will we fix the ducks limp? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-09 13:56 +0300
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 13:19 +0200
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-09 13:17 +0100
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-09 14:59 +0200
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-06 18:37 +1200
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-07 02:19 +1000
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-06 12:57 -0400
Re: I'm wrong or Will we fix the ducks limp? Steven D'Aprano <steve@pearwood.info> - 2016-06-07 04:59 +1000
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-06 17:13 -0400
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-07 00:47 +0300
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 19:03 +1200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-07 10:56 +0300
Re: I'm wrong or Will we fix the ducks limp? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-07 11:41 +0300
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-07 11:49 +0100
Re: I'm wrong or Will we fix the ducks limp? Random832 <random832@fastmail.com> - 2016-06-07 11:14 -0400
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-08 17:59 +1200
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 18:33 +1200
Re: I'm wrong or Will we fix the ducks limp? Chris Angelico <rosuav@gmail.com> - 2016-06-07 16:55 +1000
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-06 22:55 +0100
Re: I'm wrong or Will we fix the ducks limp? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 18:20 +1200
Re: I'm wrong or Will we fix the ducks limp? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-06 11:23 +0200
Re: I'm wrong or Will we fix the ducks limp? Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 13:10 +0300
Re: I'm wrong or Will we fix the ducks limp? Chris Angelico <rosuav@gmail.com> - 2016-06-06 21:57 +1000
Re: I'm wrong or Will we fix the ducks limp? BartC <bc@freeuk.com> - 2016-06-06 13:35 +0100
Re: I'm wrong or Will we fix the ducks limp? Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-05 18:25 -0700
Re: I'm wrong or Will we fix the ducks limp? Peter Pearson <pkpearson@nowhere.invalid> - 2016-06-03 16:05 +0000
Re: I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 16:09 -0700
Re: I'm wrong or Will we fix the ducks limp? cs@zip.com.au - 2016-06-06 08:41 +1000
Re: I'm wrong or Will we fix the ducks limp? Nagy László Zsolt <gandalf@shopzeus.com> - 2016-06-03 18:11 +0200
Re: I'm wrong or Will we fix the ducks limp? Sayth Renshaw <flebber.crue@gmail.com> - 2016-06-03 16:11 -0700
Re: I'm wrong or Will we fix the ducks limp? Terry Reedy <tjreedy@udel.edu> - 2016-06-03 22:12 -0400
Re: I'm wrong or Will we fix the ducks limp? jfine2358@gmail.com - 2016-06-06 07:32 -0700
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