Re: [Python-Dev] Fwd: Problem withthe API for str.rpartition()

2006-09-05 Thread Jiwon Seo 
On 9/5/06, Barry Warsaw [EMAIL PROTECTED] wrote:
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 On Sep 5, 2006, at 2:06 PM, Raymond Hettinger wrote:

  Then shouldn't rpartition be S.rpartition(sep) - (rest, sep, tail)
 
  Gads, the cure is worse than the disease.
 
  car and cdr are starting to look pretty good ;-)

 LOL, the lisper in me likes that too, but I don't think it'll work. :)


but when it comes to cadr, cddr, cdar... ;^)

I personally prefer  (left, sep, right ) since it's most clear and
there are many Python programmers whose first language is not English.

 Fred's disagreement notwithstanding, I still like (left, sep, right),
 but another alternative comes to mind after actually reading the
 docstring for rpartition wink: (before, sep, after).  Now, that's
 not ambiguous is it?  Seems to work for both partition and rpartition.

 - -Barry

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Re: [Python-Dev] problem with genexp

2006-02-20 Thread Jiwon Seo 
Regarding this Grammar change;  (last October)
 from   argument: [test '=' ] test [gen_for]
 to  argument: test [gen_for] | test '=' test ['(' gen_for ')']

- to raise error for bar(a = i for i in range(10)) )

I think we should change it to
 argument: test [gen_for] | test '=' test

instead of
 argument: test [gen_for] | test '=' test ['(' gen_for ')']

that is, without ['(' gen_for ')'] . We don't need that extra term,
because test itself includes generator expressions - with all those
parensises.
Actually with that extra ['(' gen_for ')'] ,   foo(a= 10 (for y in
'a')) is grammartically correct ; although that error seems to be
checked elsewhere.

I tested without ['(' gen_for ')'] , and worked fine passing
Lib/test/test_genexps.py

-Jiwon

On 10/20/05, Neal Norwitz [EMAIL PROTECTED] wrote:
 On 10/16/05, Neal Norwitz [EMAIL PROTECTED] wrote:
  On 10/10/05, Neal Norwitz [EMAIL PROTECTED] wrote:
   There's a problem with genexp's that I think really needs to get
   fixed.  See http://python.org/sf/1167751 the details are below.  This
   code:
  
foo(a = i for i in range(10))
  
   I agree with the bug report that the code should either raise a
   SyntaxError or do the right thing.
 
  The change to Grammar/Grammar below seems to fix the problem and all
  the tests pass.  Can anyone comment on whether this fix is
  correct/appropriate?  Is there a better way to fix the problem?

 Since no one responded other than Jiwon, I checked in this change.  I
 did *not* backport it since what was syntactically correct in 2.4.2
 would raise an error in 2.4.3.  I'm not sure which is worse.  I'll
 leave it up to Anthony whether this should be backported.

 BTW, the change was the same regardless of old code vs. new AST code.

 n
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Re: [Python-Dev] Let's just *keep* lambda

2006-02-09 Thread Jiwon Seo 
On 2/8/06, Martin v. Löwis [EMAIL PROTECTED] wrote:
 Jiwon Seo wrote:
  Then, is there any chance anonymous function - or closure - is
  supported in python 3.0 ? Or at least have a discussion about it?

 That discussion appears to be closed (or, not really: everybody
 can discuss, but it likely won't change anything).

  (IMHO, closure is very handy for function like map, sort etc. And
  having to write a function for multiple statement is kind of good in
  that function name explains what it does. However, I sometimes feel
  that having no name at all is clearer. Also, having to define a
  function when it'll be used only once seemed inappropriate sometimes.)

 Hmm. Can you give real-world examples (of existing code) where you
 needed this?

Apparently, simplest example is,

collection.visit(lambda x: print x)

which currently is not possible. Another example is,

map(lambda x: if odd(x): return 1
  else: return 0,
listOfNumbers)

(however, with new if/else expression, that's not so much a problem any more.)

Also, anything with exception handling code can't be without explicit
function definition.

collection.visit(lambda x: try: foo(x); except SomeError: error(error
message))

Anyway, I was just curious that if anyone is interested in having more
closure-like closure in python 3.0 - in any form, not necessary an
extension on lambda.

-Jiwon


 Regards,
 Martin

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Re: [Python-Dev] Let's just *keep* lambda

2006-02-08 Thread Jiwon Seo 
On 2/8/06, Guido van Rossum [EMAIL PROTECTED] wrote:
 On 2/8/06, Patrick Collison [EMAIL PROTECTED] wrote:
  And to think that people thought that keeping lambda, but changing
  the name, would avoid all the heated discussion... :-)

 Note that I'm not participating in any attempts to improve lambda.

Then, is there any chance anonymous function - or closure - is
supported in python 3.0 ? Or at least have a discussion about it?

(IMHO, closure is very handy for function like map, sort etc. And
having to write a function for multiple statement is kind of good in
that function name explains what it does. However, I sometimes feel
that having no name at all is clearer. Also, having to define a
function when it'll be used only once seemed inappropriate sometimes.)

or is there already discussion about it (and closed)?

-Jiwon

-Jiwon


 Just about the only improvement I'd like to see is to add parentheses
 around the arguments, so you'd write lambda(x, y): x**y instead of
 lambda x, y: x**y.

 --
 --Guido van Rossum (home page: http://www.python.org/~guido/)
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Re: [Python-Dev] Let's just *keep* lambda

2006-02-08 Thread Jiwon Seo 
On 2/8/06, Josiah Carlson [EMAIL PROTECTED] wrote:

 Jiwon Seo [EMAIL PROTECTED] wrote:
 
  On 2/8/06, Guido van Rossum [EMAIL PROTECTED] wrote:
   On 2/8/06, Patrick Collison [EMAIL PROTECTED] wrote:
And to think that people thought that keeping lambda, but changing
the name, would avoid all the heated discussion... :-)
  
   Note that I'm not participating in any attempts to improve lambda.
 
  Then, is there any chance anonymous function - or closure - is
  supported in python 3.0 ? Or at least have a discussion about it?
 
  or is there already discussion about it (and closed)?

 Closures already exist in Python.

  def foo(bar):
 ... return lambda: bar + 1
 ...
  a = foo(5)
  a()
 6

Not in that we don't have anonymous function (or closure) with
multiple statements. Also, current limited closure does not capture
programming context - or variables.

-Jiwon
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Re: [Python-Dev] Let's just *keep* lambda

2006-02-07 Thread Jiwon Seo 
On 2/6/06, Christopher Armstrong [EMAIL PROTECTED] wrote:
 On 2/7/06, Martin v. Löwis [EMAIL PROTECTED] wrote:
  Brett Cannon wrote:
   But I know that everyone and their email client is against me on this
   one, so I am not going to really try to tear into this.  But I do
   think that lambda needs a renaming.  Speaking as someone who still
   forgets that Python's lambda is not the same as those found in
   functional languages
 
  Can you elaborate on that point? I feel that Python's lambda is exactly
  the same as the one in Lisp. Sure, the Lisp lambda supports multiple
  sequential expressions (the progn feature), but I understand that
  this is just an extension (although one that has been around several
  decades).
 
  Of course, Python's expressions are much more limited as Lisp's (where
  you really can have macros and special forms in as the expression
  in a lambda), but the lambda construct itself seems to be the very
  same one.

 If we phrase it somewhat differently, we can see that lambdas are
 different in Python and Lisp, in a very practical way. First:
 Everything in Lisp is an expression. There's no statement, in Lisp,
 that isn't also an expression. Lambdas in Lisp can contain arbitrary
 expressions; therefore you can put any language construct inside a
 lambda. In Python, you cannot put any language construct inside a
 lambda. Python's and Lisp's lambdas are effectively totally different.

 +1 on keeping Lambda, +1 on making it more useful.

After lambda being made more useful, can I hope that I will be able to
use lambda with multiple statements? :) Lambdas in Lisp and Python are
different, but in the usability perspective they don't need to differ
too much.

-Jiwon
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Re: [Python-Dev] problem with genexp

2005-10-17 Thread Jiwon Seo 
On 10/16/05, Neal Norwitz [EMAIL PROTECTED] wrote:
 On 10/10/05, Neal Norwitz [EMAIL PROTECTED] wrote:
  There's a problem with genexp's that I think really needs to get
  fixed.  See http://python.org/sf/1167751 the details are below.  This
  code:
 
   foo(a = i for i in range(10))
 
  I agree with the bug report that the code should either raise a
  SyntaxError or do the right thing.

 The change to Grammar/Grammar below seems to fix the problem and all
 the tests pass.  Can anyone comment on whether this fix is
 correct/appropriate?  Is there a better way to fix the problem?

 -argument: [test '='] test [gen_for] # Really [keyword '='] test
 +argument: test [gen_for] | test '=' test ['(' gen_for ')'] # Really
 [keyword '='] test

The other option would be changes in the Python/compile.c (somewhat)
like following

diff -r2.352 compile.c
6356c6356,6362
-   if (TYPE(n) == argument  NCH(n) == 3) {
---
+   if (TYPE(n) == argument  NCH(n) == 4) {
+   PyErr_SetString(PyExc_SyntaxError,
+   invalid syntax);
+   symtable_error(st, n-n_lineno);
+   return;
+   }
+   else if (TYPE(n) == argument  NCH(n) == 3) {

but IMO, changing the Grammar looks more obvious.


 n
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