Re: Common LISP-style closures with Python
在 2012年2月4日星期六UTC+8上午8时27分56秒，Antti J Ylikoski写道： In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: - # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 - and now we can do: - a=f1() b=f1() a() 1 a() 2 a() 3 a() 4 b() 1 b() 2 a() 5 b() 3 b() 4 - i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. yours, Antti J Ylikoski Helsinki, Finland, the EU We are not in the 1990's now. A descent CAD or internet application now should be able to support users with at least one or more script languages easily. Whether it's javascript or java or flash in the browser-based applications, or go, python in the google desktop API, commercial SW applications to be able to evolve in the long run are not jobs from the publishers and the original writers of the SW packages only. I don't want to include a big fat compiler in my software, what else can I do ? LISP is too fat, too. -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 2/3/2012 4:27 PM, Antti J Ylikoski wrote: In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: Most dynamic languages have closures. Even Perl and Javascript have closures. Javascript really needs them, because the callback orientation of Javascript means you often need to package up state and pass it into a callback. It really has very little to do with functional programming. If you want to see a different style of closure, check out Rust, Mozilla's new language. Rust doesn't have the spaghetti stack needed to implement closures, so it has more limited closure semantics. It's more like some of the C add-ons for closures, but sounder. John Nagle -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Feb 3, 6:27 pm, Antti J Ylikoski antti.yliko...@tkk.fi wrote: In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: [...] do my eyes not see nor my ears not hear? a thread about common Lisp and Xan Lee is not near? would someone please him wake up and tell him all about, the thread titled Common LISP-style closures with Python and that he has been left out! -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 02/05/2012 05:19 AM, Antti J Ylikoski wrote: Yes, I do know that, but then it would not be a closure :-) Forgive me if this is terribly naive, but what is the advantage of using a closure as opposed to, say, some other function that returns the same value in the same context, but is not a closure? Alan -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Sat, Feb 4, 2012 at 9:19 PM, Antti J Ylikoski antti.yliko...@tkk.fi wrote: I'm not sure how naughty this is, but the same thing can be done without using nonlocal by storing the local state as an attribute of the enclosed function object: ... Yes, I do know that, but then it would not be a closure :-) Sure it is. Where do you think it looks up the function object? Cheers, Ian -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 5.2.2012 22:58, Ian Kelly wrote: On Sat, Feb 4, 2012 at 9:19 PM, Antti J Ylikoskiantti.yliko...@tkk.fi wrote: I'm not sure how naughty this is, but the same thing can be done without using nonlocal by storing the local state as an attribute of the enclosed function object: ... Yes, I do know that, but then it would not be a closure :-) Sure it is. Where do you think it looks up the function object? Cheers, Ian OK, thank you for correcting me. Andy -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 4.2.2012 4:47, Chris Rebert wrote: On Fri, Feb 3, 2012 at 4:27 PM, Antti J Ylikoskiantti.yliko...@tkk.fi wrote: In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: - # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 snip i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris I understand that a closure is something which is typical of functional programming languages. -- Scheme-style closures, for example. I don't know Haskell, ML etc. but I do suspect that we could create closures in those languages as well. Maybe someone more expert than me can help? regards, Andy -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 4.2.2012 12:14, Antti J Ylikoski wrote: On 4.2.2012 4:47, Chris Rebert wrote: On Fri, Feb 3, 2012 at 4:27 PM, Antti J Ylikoskiantti.yliko...@tkk.fi wrote: In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: - # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 snip i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris I understand that a closure is something which is typical of functional programming languages. -- Scheme-style closures, for example. I don't know Haskell, ML etc. but I do suspect that we could create closures in those languages as well. Maybe someone more expert than me can help? regards, Andy This is how it is done in standard Common LISP: - ;;; Closure with Common LISP. ;;; ;;; Antti J Ylikoski 02-03-2012. (defun mak-1 () (let ((n 0)) #'(lambda () (incf n - kind regards, Andy -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 4 February 2012 10:14, Antti J Ylikoski antti.yliko...@tkk.fi wrote: On 4.2.2012 4:47, Chris Rebert wrote: Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris I understand that a closure is something which is typical of functional programming languages. -- Scheme-style closures, for example. I don't know Haskell, ML etc. but I do suspect that we could create closures in those languages as well. Maybe someone more expert than me can help? I think what Chris asking is: what is the feature of Common-Lisp closures that Python closures share but other languages don't? I think what he is implying is that there is no such feature. Python closures are no more Common-Lisp-style than they are Scheme-style or Smalltalk-like or any other language-like. -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 4.2.2012 12:58, Arnaud Delobelle wrote: On 4 February 2012 10:14, Antti J Ylikoskiantti.yliko...@tkk.fi wrote: On 4.2.2012 4:47, Chris Rebert wrote: Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris I understand that a closure is something which is typical of functional programming languages. -- Scheme-style closures, for example. I don't know Haskell, ML etc. but I do suspect that we could create closures in those languages as well. Maybe someone more expert than me can help? I think what Chris asking is: what is the feature of Common-Lisp closures that Python closures share but other languages don't? I think what he is implying is that there is no such feature. Python closures are no more Common-Lisp-style than they are Scheme-style or Smalltalk-like or any other language-like. I would say that Python closures are equivalent with Common LISP closures (except that LAMBDA is more limited in Python, which is a feature which I don't like.) Do you maybe mean non-Common-LISP-style closures in Python? I cannot think of any ones. kind regards, Andy -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Sat, 4 Feb 2012, Antti J Ylikoski wrote: On 4.2.2012 12:58, Arnaud Delobelle wrote: On 4 February 2012 10:14, Antti J Ylikoskiantti.yliko...@tkk.fi wrote: On 4.2.2012 4:47, Chris Rebert wrote: Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris I understand that a closure is something which is typical of functional programming languages. -- Scheme-style closures, for example. I don't know Haskell, ML etc. but I do suspect that we could create closures in those languages as well. Maybe someone more expert than me can help? I think what Chris asking is: what is the feature of Common-Lisp closures that Python closures share but other languages don't? I think what he is implying is that there is no such feature. Python closures are no more Common-Lisp-style than they are Scheme-style or Smalltalk-like or any other language-like. I would say that Python closures are equivalent with Common LISP closures (except that LAMBDA is more limited in Python, which is a feature which I don't like.) Do you maybe mean non-Common-LISP-style closures in Python? I cannot think of any ones. kind regards, Andy AFAIK there is only one style for closure, similar to one style for square. There are quite a lot languages implementing closures, and quite a lot try to imitate them, including C with non-standard extension (without using those imitations I cannot say if they are good enough). http://en.wikipedia.org/wiki/Closure_(computer_science) Wrt lambdas, I really like blocks from Ruby (which AFAIK stem from blocks in Smalltalk, not sure if they call them blocks). http://lesscode.org/2005/07/12/ruby-colored-blocks-in-python/ http://railsguru.org/2010/03/learn-ruby-procs-blocks-lambda/ I mean, myself I am ok with lambdas (using them in languages where lambda is welcomed and contributing citizen) but blocks in place of lambdas would be nice to have in Python. Introduction of with construct was good IMHO, but if one likes coding style relying on passing anonymous pieces of code then Python might not be good choice for this. On the other hand, one can argue that using anonymous code too much is not the best style. I am not sure if extensive use of blocks/lambdas really helps, or if it contributes to clever hacks and a source of maintainance pain. So, perhaps it is good to have it in a few different ways - like, Ruby, Python and CL - and experiment with them all. In other words, rather than talking about making Python more like some other language(s) I think it is much better to learn those other language(s). If you'd like to try unlimited lambda, you might want to play with Racket, a Scheme superset. Or any other Scheme - it's simple enough to start coding after a day or two of learning (I mean Fibonaccis and Erastotenes sieves, not implementing database or web server). Myself, I would rather have blocks/lambdas and not need them rather than the other way, but that's just me. Regards, Tomasz Rola -- ** A C programmer asked whether computer had Buddha's nature. ** ** As the answer, master did rm -rif on the programmer's home** ** directory. And then the C programmer became enlightened... ** ** ** ** Tomasz Rola mailto:tomasz_r...@bigfoot.com ** -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Sat, Feb 4, 2012 at 5:58 AM, Arnaud Delobelle arno...@gmail.com wrote: I think what Chris asking is: what is the feature of Common-Lisp closures that Python closures share but other languages don't? I think what he is implying is that there is no such feature. Python closures are no more Common-Lisp-style than they are Scheme-style or Smalltalk-like or any other language-like. No such feature? What's that nonlocal thing then? The above function could not be written that way in Python 2. Of course maybe we want to put this feature in another category, but anyway, the function couldn't be written in some languages, even though they have closures. -- Devin -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Sat, 04 Feb 2012 02:27:56 +0200 Antti J Ylikoski antti.yliko...@tkk.fi wrote: [...] # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 [...] i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. I'm not sure how naughty this is, but the same thing can be done without using nonlocal by storing the local state as an attribute of the enclosed function object: def f(): ... def g(): ... g.count += 1 ... return g.count ... g.count = 0 ... return g ... h = f() j = f() h() 1 h() 2 h() 3 j() 1 j() 2 j() 3 This way, you can also write to the attribute: j.count = 0 j() 1 John -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On 5.2.2012 3:31, John O'Hagan wrote: On Sat, 04 Feb 2012 02:27:56 +0200 Antti J Ylikoskiantti.yliko...@tkk.fi wrote: [...] # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 [...] i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. I'm not sure how naughty this is, but the same thing can be done without using nonlocal by storing the local state as an attribute of the enclosed function object: def f(): ... def g(): ... g.count += 1 ... return g.count ... g.count = 0 ... return g ... h = f() j = f() h() 1 h() 2 h() 3 j() 1 j() 2 j() 3 This way, you can also write to the attribute: j.count = 0 j() 1 John Yes, I do know that, but then it would not be a closure :-) Andy -- http://mail.python.org/mailman/listinfo/python-list
Common LISP-style closures with Python
In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: - # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 - and now we can do: - a=f1() b=f1() a() 1 a() 2 a() 3 a() 4 b() 1 b() 2 a() 5 b() 3 b() 4 - i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. yours, Antti J Ylikoski Helsinki, Finland, the EU -- http://mail.python.org/mailman/listinfo/python-list
Re: Common LISP-style closures with Python
On Fri, Feb 3, 2012 at 4:27 PM, Antti J Ylikoski antti.yliko...@tkk.fi wrote: In Python textbooks that I have read, it is usually not mentioned that we can very easily program Common LISP-style closures with Python. It is done as follows: - # Make a Common LISP-like closure with Python. # # Antti J Ylikoski 02-03-2012. def f1(): n = 0 def f2(): nonlocal n n += 1 return n return f2 snip i. e. we can have several functions with private local states which are kept between function calls, in other words we can have Common LISP-like closures. Out of curiosity, what would be non-Common-Lisp-style closures? Cheers, Chris -- http://mail.python.org/mailman/listinfo/python-list
