Alan Gauld wrote:
However, Python doesn't need lambdas to be able to write in a functional style.
I disagree Jeff. It does need lambdas to do FP properly, and better lambdas than we have currently. What it doesn't need is the lambda keyword and syntax - although pesonally I like lambda since it is descriptive!
Well, we'll have to continue to disagree on that. ;) Personally, I can't help but think that 'lambda' is descriptive only to people who've experienced it elsewhere, and that that does *not* include the majority of the programming community, but I could be mistaken. :)
Functions are first-class objects and can be passed around quite easily,
Yes, but lambdas are more than first class functions, they are anonymous functions! In fact really just callable code blocks, not necessarily functions in the strictest sense (except that every callable in FP is a function...! ;-)
Well, given that in Python a function is just a callable code block that's bound to a name... ;) Personally, I fail to see why having an anonymous function is such a huge conceptual advantage, no matter how many times this is proclaimed as truth by lambda-users, but again this is just my own impression.
Having to define every function before using it would be a big hassle and make code less readable IMHO.
Here, ISTM that you're emphasizing the in-line nature of lambdas as being their key usage point... And personally, I prefer to have a glossary of terms rather than having to decipher jargon by context. ;)
only a few differences between lambdas and named functions in Python:
- Anonymous vs named
the key feature
Again, I fail to see why this is such an advantage -- I've seen assertions that it is, over and over again, but never any convincing evidence....
- Single expression vs suite of statements
A python restriction.
Well, I *did* specify that I was talking about 'in Python'... ;)
I'd also argue that the inline nature is the *true* differentiating feature of lambdas -- the fact that they're anonymous is relatively minor.
I agree, if I had an inline mechanism that forced me to provide a name I could just use 'f' over and over and not feel too cheated, but its nicer not to have an artificial name when theres no need.
Personally, I prefer to have the opportunity to provide a meaningful name, and don't see where a generic name is any more restrictive than having no name, but again, maybe that's just me.
So, while there are some advantages to having single-use callables be defined inline
The other advantage is the huge conceptial advantage that real lambdas confer. The breakthrough idea of
def f(x): return x+x
being the same as
f = lambda x: x+x
is only possible to demonstrate if you have lambda to start with. And yet that concept of a function name being just another variable and the callable code being an object in its own right becomes much more obvious in my opinion. lambda is a learning tool which shows what is really happening whereas def is just syntactic sugar.
Hm, I understood the idea of functions being just code objects that were bound to a name, and could be passed around, stored in collections, and effectively renamed, well before I really got a hold on lambdas as anything more than some confusing bit of magic. Of course, I started in C, where I was fairly comfortable with the idea of function pointers; function objects are a pretty simple step up, abstraction-wise, from that.
I suppose that one might argue that I *still* just don't really get lambdas (and I wouldn't argue with that). I can see some advantages to small inline functions, though I suspect that a more-explicit currying mechanism (such as the proposed partial() higher-order function) could easily replace such uses. I'm sorry to say, though, that the supposed advantages of anonymity come across as little more than handwaving assertions to me, no matter how sincerely they're intended. (I've just started to read through SICP, to pick up some lisp/scheme, in hopes of understanding the appeal a bit better, so maybe there's hope for me yet. ;) )
Jeff Shannon Technician/Programmer Credit International
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