This is the first time I write something that looks like a little rant :-) Surely I'll be wrong in many points, but I presume this isn't going to damage people, so...
Here there are some functional Python solutions to some Euler problems: http://pyeuler.wikidot.com/ Some pieces of that code: def takenth(n, iterable): "Returns the nth item" return list(islice(iterable, n, n+1))[0] def euler1(end, nums): isanymultiple = lambda x: any((x % y == 0) for y in nums) return sum(filter(isanymultiple, xrange(end))) euler1(1000, [3,5]) #Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed one million. def fibonacci(n): """Return nth element of the fibonacci serie""" if n == 0 or n == 1: return n return fibonacci(n-1) + fibonacci(n-2) def euler2(end): genfib = imap(fibonacci, count()) candidates = takewhile(lambda n: n<end, genfib) return sum(ifilter(lambda n: n%2, candidates)) def least_common_multiple(nums): """Return least common multiples of nums""" factorized = dict((n, dict(factorize(n))) for n in nums) union = lambda lst: reduce(set.union, map(set, lst)) all_factors = union(factorized.values()) getexponent = lambda factor: (factorized[n].get(factor, 0) for n in nums) return mul(factor**(max(getexponent(factor))) for factor in all_factors) What I think about such code: - It's not much readable (but usually it can be read). - it's not much Pythonic. Python is only partially functional, if you try to use it in a very functional way you go against the language, its coding practices, and the net result may be slow/little readable. If you want to write almost fully functional code it's better to use a fitter language, like Haskell. - In some situations it seems to just show lack of knowledge of Python. - In various points it's not much efficient in speed and/or space. - It's not even short, there are many ways to shorten that code, often keeping or even increasing its readability; one of the most common ways is to use generators and list comps more often. - It lacks tests, like doctests. - It has small pedagogical value too, because this is a bad way to learn Python, and programming in general too. - It has shown me when to use takewhile(), and some of the mathematical insights it contains are interesting :-) Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
