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Re: pygame - importing GL - very bad...

References (6 earlier) <kc7uia$8h1$1@dont-email.me> <mailman.104.1357349785.2939.python-list@python.org> <kc90g4$p5d$1@dont-email.me> <mailman.111.1357386440.2939.python-list@python.org> <kc98gm$21c$1@dont-email.me>
Date 2013-01-06 00:27 +1100
Subject Re: pygame - importing GL - very bad...
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.115.1357392442.2939.python-list@python.org> (permalink)

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On Sun, Jan 6, 2013 at 12:06 AM, someone <newsboost@gmail.com> wrote:
> On 01/05/2013 12:47 PM, Chris Angelico wrote:
>> You can find good references on the subject in various
>> places, but call-by-reference as implemented in Pascal simply doesn't
>> exist in most modern languages, because its semantics are way
>> confusing. The name given to this technique varies; here's a couple of
>> links:
>>
>> http://effbot.org/zone/call-by-object.htm
>> http://en.wikipedia.org/wiki/Evaluation_strategy#Call_by_sharing
>
> If you don't like calling it "pass-by-reference", perhaps you prefer calling
> it: “call by object reference“...  From:
> http://effbot.org/zone/call-by-object.htm
>
> In any case I think we understand each other.

That's one of the links I just posted :) It's not just a naming
difference, though. With Pascal's pass-by-reference semantics, this
code would act differently:

def foo(x):
  x = 5

a = 2
foo(a)
print(a)

Python prints 2, because the assignment to x just rebinds the name
inside foo. True pass-by-reference actually changes the caller's
variable. C can achieve this by means of pointers; in Python, you can
pass and mutate a list, thus:

def foo(x):
  x[0] = 5 # Dereference the pointer, kinda

x=[None] # Declare a pointer variable, ish
x[0] = 2
foo(x) # Don't forget to drop the [0] when passing the pointer to
another function
print(x[0]) # Prints 5. See? We have pass-by-reference!

But otherwise, rebinding names in the function has no effect on
anything outside. Among other things, this guarantees that, in any
situation, a name referencing an object can be perfectly substituted
for any other name referencing the same object, or any other way of
accessing the object.

def foo(lst):
  lst[0]=len(lst)

x = [10,20,30]
y = x
foo(x) # These two...
foo(y) # ... are identical!

This is a philosophy that extends through the rest of the language. A
function returning a list can be directly dereferenced, as can a list
literal:

def foo():
  return [0,1,4,9,16]

print( ["Hello","world!","Testing","Testing","One","Two","Three"][foo()[2]] )

This is a flexibility and power that just doesn't exist in many older
languages (C and PHP, I'm looking at you). Object semantics make more
sense than any other system for a modern high level language, which is
why many of them do things that way.

ChrisA

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Thread

pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-01 12:00 +0100
  Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-01 22:13 +1100
    Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 00:49 +0100
      Re: pygame - importing GL - very bad... Michael Torrie <torriem@gmail.com> - 2013-01-02 14:57 -0700
        Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 02:53 +0100
          Re: pygame - importing GL - very bad... "Mike C. Fletcher" <mcfletch@vrplumber.com> - 2013-01-03 09:09 -0500
            Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 02:10 +0100
              Re: pygame - importing GL - very bad... Dave Angel <d@davea.name> - 2013-01-04 20:30 -0500
                Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 11:49 +0100
                Re: pygame - importing GL - very bad... Dave Angel <d@davea.name> - 2013-01-05 06:23 -0500
                Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-05 22:47 +1100
                Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 14:06 +0100
                Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-06 00:27 +1100
                Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 20:49 +0100
                Re: pygame - importing GL - very bad... alex23 <wuwei23@gmail.com> - 2013-01-06 03:37 -0800
                Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-06 13:46 +0100
      Re: pygame - importing GL - very bad... Andrew Berg <bahamutzero8825@gmail.com> - 2013-01-02 16:30 -0600
        Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 03:02 +0100
  Re: pygame - importing GL - very bad... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-01 11:49 +0000
    Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 00:49 +0100
      Re: pygame - importing GL - very bad... Nobody <nobody@nowhere.com> - 2013-01-02 03:01 +0000
        Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 04:43 +0100
        Re: pygame - importing GL - very bad... alex23 <wuwei23@gmail.com> - 2013-01-02 01:52 -0800
          Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 15:04 +0100
      Re: pygame - importing GL - very bad... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-02 07:39 +0000
        Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 15:06 +0100
  Re: pygame - importing GL - very bad... Peter Otten <__peter__@web.de> - 2013-01-01 13:56 +0100
    Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 00:50 +0100
      pylint, was Re: pygame - importing GL - very bad... Peter Otten <__peter__@web.de> - 2013-01-02 13:07 +0100
        Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 15:09 +0100
          Re: pylint, was Re: pygame - importing GL - very bad... Dave Angel <d@davea.name> - 2013-01-02 09:26 -0500
            Re: pylint, was Re: pygame - importing GL - very bad... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-02 23:52 +0000
              Re: pylint, was Re: pygame - importing GL - very bad... Ian Kelly <ian.g.kelly@gmail.com> - 2013-01-02 17:25 -0700
              Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 03:24 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... Terry Reedy <tjreedy@udel.edu> - 2013-01-02 21:48 -0500
                Re: pylint, was Re: pygame - importing GL - very bad... Ian Kelly <ian.g.kelly@gmail.com> - 2013-01-02 19:55 -0700
                Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 12:19 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-03 22:27 +1100
                Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 02:11 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... Jan Riechers <janpeterr@freenet.de> - 2013-01-05 14:49 +0200
                Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 14:09 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... Ben Finney <ben+python@benfinney.id.au> - 2013-01-03 17:01 +1100
                Re: pylint, was Re: pygame - importing GL - very bad... Chris Rebert <clp2@rebertia.com> - 2013-01-02 22:33 -0800
                Re: pylint, was Re: pygame - importing GL - very bad... Peter Otten <__peter__@web.de> - 2013-01-03 10:00 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 12:21 +0100
                Regular expression syntax, was Re: pylint, was Re: pygame - importing GL - very bad... Peter Otten <__peter__@web.de> - 2013-01-03 12:39 +0100
                Re: Regular expression syntax, was Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 02:12 +0100
                Re: pylint, was Re: pygame - importing GL - very bad... "Mike C. Fletcher" <mcfletch@vrplumber.com> - 2013-01-03 09:19 -0500
                Re: pylint, was Re: pygame - importing GL - very bad... Terry Reedy <tjreedy@udel.edu> - 2013-01-03 11:52 -0500
                Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 02:14 +0100
            Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 03:06 +0100
      Re: pylint, was Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-03 01:32 +1100
      Re: pylint, was Re: pygame - importing GL - very bad... Ian Kelly <ian.g.kelly@gmail.com> - 2013-01-02 10:52 -0700
      Re: pylint, was Re: pygame - importing GL - very bad... Chris Angelico <rosuav@gmail.com> - 2013-01-03 04:57 +1100
      Re: pylint, was Re: pygame - importing GL - very bad... Ian Kelly <ian.g.kelly@gmail.com> - 2013-01-02 12:31 -0700
        Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-03 03:31 +0100
          Re: pylint, was Re: pygame - importing GL - very bad... Dave Angel <d@davea.name> - 2013-01-02 21:56 -0500
            Re: pylint, was Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-05 02:23 +0100
  Re: pygame - importing GL - very bad... alex23 <wuwei23@gmail.com> - 2013-01-01 14:39 -0800
    Re: pygame - importing GL - very bad... someone <newsboost@gmail.com> - 2013-01-02 00:56 +0100

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