Let's Talk About Lambda Functions!
bokr at oz.net
Thu Aug 1 22:14:42 CEST 2002
On Tue, 30 Jul 2002 19:22:50 -0400, "John Roth" <johnroth at ameritech.net> wrote:
>"Ian Bicking" <ianb at colorstudy.com> wrote in message
>news:mailman.1028054866.6584.python-list at python.org...
>> On Tue, 2002-07-30 at 11:05, John Roth wrote:
>> > I tend to agree with you on that one, but it's a matter of style. I
>> > observe
>> > that e.g. Smalltalk style does anonymous code blocks all over the
>> I've seen people argue that you can do all the same things with
>> iterators as Smalltalk does with code blocks. And, really, it's not
>> though Smalltalk has truly novel control structures -- everything
>> boils down to while, for, and if. Smalltalk does give you easy
>> callbacks, though.
>> > There's no reason my proposal couldn't be extended to anonymous
>> > classes: the syntactic issues are exactly the same. The difficulty
>> > in extending it to methods, as opposed to functions. The only way
>> > to distinguish a method from a function today is to observe that
>> > methods are defined at the top level of a class; a def anywhere
>> > else is a function (I think.)
>> A method is just a function that is bound to a class variable. So you
>> can do something like:
>> class X:
>> X.func = lambda self, x: x * 2
>> x = X()
>> ==> 20
>> In fact, you can even do:
>> class X:
>> func = lambda self, x: x * 2
>Unfortunately, that won't work. The word 'self' is not
>magic - using it doesn't convert a function to a method.
No, but making it a class attribute seems to do the magic
(which can also be modified with staticmethod and classmethod).
It works on Python 2.2 (#28, Dec 21 2001, 12:21:22) [MSC 32 bit (Intel)] on win32
However, 'self' in this example is not even used except to get the
instance bound to it and be ignored.
>>> class X: pass
>>> X.func = lambda self,x: x*2
>>> class X:
... func = lambda self,x: x*2
>On the other hand, if 'self' was the name assigned
>to the instance in the enclosing method definition, it
>would acomplish just about everything required. I suspect
>there are a few corner cases it wouldn't handle, to
>the confusion of all and sundry.
UIAM, it (self) is just a conventional parameter name to bind
the instance object implicitly passed to the method function
as a first parameter.
>>> class X:
... def __init__(ego, v): ego.v = v
... func = lambda lego: '<%s with v=%s>' %(lego,lego.v)
'<<__main__.X instance at 0x007CF780> with v=123>'
>Someone who knows the language in more depth
>than I do would have to comment on that.
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