On Mon, May 10, 2010 at 08:45:51PM +0100, Nobody wrote: > On Tue, 11 May 2010 00:24:22 +1200, Samuel Williams wrote: > > Is Python a functional programming language? > Not in any meaningful sense of the term.
LOL > > I heard that lambdas were limited to a single expression, > > Yes. In a functional language that wouldn't be a problem, as there's no > limit to the complexity of an expression. Python's expressions are far > more limited, which restricts what can be done with a lambda. One very annoying thing in Python is the distinction between statements and expressions. Ever since learning LISP (well, Scheme) in S&ICP I find myself frequently annoyed by this pointless distinction, started by C (or earlier), and propogated without much thought. Often I'll want to write a lamda that, say, prints something, or modifies a global variable, and find that, well, it's either impossible or beyond my interest in figuring it out. It appears there is finally a ternary operator (for making if/else into "expressions"): http://en.wikipedia.org/wiki/Ternary_operation#Python Maybe it will grow on me - it makes sense in English, but on first glance I thought the programmer suffered from dyslexia. To be fair, it appears that Python's whitespace-sensitive syntax sort of precludes the "make a complex function on one line" that is typical of languages which don't have statement/expression distinctions, but I'm not convinced it couldn't be solved, perhaps by allowing anonymous functions to span multiple lines, just like named functions. > > Finally, even if Python supports functional features, is this a model that > > is used often in client/application code? > > Not really. List comprehensions are probably the most common example of > functional idioms, but again they're limited by Python's rather limited > concept of an expression. Map/reduce, lambda, apply, that kind of stuff... kinda similar to functional languages. But "statements lack any side effects"? No way. In fact, a common distinction you'll see observed, but not always, is that "statements may have side effects, expressions do not". For some definitions of "functional language", there are no side-effects, so there is no need for a statement which doesn't evaluate to a value, so there is no need for a statement/expression distinction, so everything is an expression. You may have seen Paul Graham's other article about Python and LISP: http://www.paulgraham.com/icad.html Upon re-skimming it, I find myself wondering if I got the expression/statement annoyance from his pages, or from my own experience. I can't remember :-) Probably it was an annoyance that I hadn't put my finger on until he spelled it out for me, like a splinter in my mind :-) He obliquely references my other pet peeve, the global/class/local distinction, completely ignoring arbitrarily-nested lexical scoping. From what I've read in this thread, there's a recent "nonlocal" declaration that sounds like it might accomplish something useful in this regard. (I still haven't figured out how he managed to use lexical closures in his web server to allow one web page to use another to allow the user to select and return a value, like a color from a color wheel, unless he implemented his own web server in LISP, since HTTP is stateless). I really like Scheme's clean syntax (never learned Common LISP, sorry, too much to remember) but frankly, I've never looked at a problem and said, "you know, Scheme would be perfect for this". Maybe if I was writing a program that did optimizing transformations on abstract syntax trees, or something. And since Scheme has never come in handy, I never bothered with Common LISP. I feel similarly about ML, OCAML and Haskell... maybe one day when I'm bored, not today, not this project. So in the end, I find myself using python more than anything else, fully acknowledging its warts. I used to admire its simplicity, but now with decorators, iterators, generators, metaclasses, and the proliferation of special method names, I have to wonder if that still holds true... certainly I understand 90+% of python programs, but do I understand that proportion of the constructs? PS: Why do people call LISP object-oriented? Are they smoking crack? No classes, no methods, no member variables... WTF? -- A Weapon of Mass Construction My emails do not have attachments; it's a digital signature that your mail program doesn't understand. | http://www.subspacefield.org/~travis/ If you are a spammer, please email j...@subspacefield.org to get blacklisted.
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