tuples

In Scala (2.7.7final), the Predef.println method is defined as having the following signature: def println (x : Any) : Unit How come, then that the following works: scala> println(1,2) (1,2) Does the compiler automatically convert a comma-separated list of arguments into a Tuple? By what magic? Is there an implicit conversion going on here, and if so, which one? Yes, the compiler will attempt to convert comma separated arguments into tuples, if there are no appropriate multi-argument methods and a single appropriate one-argument method. It's not an implicit conversion, just a compiler hack.

Given a variadic template Types... , I would like to store A<> for each of the types in the pack. This could be done in a tuple of A<> 's, but I'd need to programmatically derive the type of said tuple. Is such a thing even possible in c++11/14/17? template <class T> class A { }; template <class... Types> class B { // A tuple of A<>'s for each type in Types... std::tuple<A<Type1>, A<Type2>, ...> data; }; Simply with: template <class... Types> class B { std::tuple<A<Types>...> data; }; 来源： https://stackoverflow.com/questions/32336822/wrapping-each-type-in-a-variadic-template-in-a-templated

How can I compare Multiple lists of tuples like this: [[(1,2), (3,6), (5,3)], [(1,5), (3,5)], [(2,1), (1,8), (3,9)]] The output should be: [(1,2), (1,5), (1,8)],[(3,6), (3,5), (3,9)] It means that i want just those values whose x-axis value matches others. (5,3) and (2,1) should be discarded! One possible Option >>> def group(seq): for k, v in groupby(sorted(chain(*seq), key = itemgetter(0)), itemgetter(0)): v = list(v) if len(v) > 1: yield v >>> list(group(some_list)) [[(1, 2), (1, 5), (1, 8)], [(3, 6), (3, 5), (3, 9)]] Another Popular Option >>> from collections import defaultdict >>> def

I have a list consisting of tuples, I want to pass each tuple's elements to a function as arguments: mylist = [(a, b), (c, d), (e, f)] myfunc(a, b) myfunc(c, d) myfunc(e, f) How do I do it? Best Regards This is actually very simple to do in Python, simply loop over the list and use the splat operator ( * ) to unpack the tuple as arguments for the function: mylist = [(a, b), (c, d), (e, f)] for args in mylist: myfunc(*args) E.g: >>> numbers = [(1, 2), (3, 4), (5, 6)] >>> for args in numbers: ... print(*args) ... 1 2 3 4 5 6 To make @DSM's comment explicit: >>> from itertools import starmap >>>

Python has (1,) for a single element tuple. In Scala, (1,2) works for Tuple2(1,2) but we must use Tuple1(1) to get a single element tuple. This may seem like a small issue but designing APIs that expect a Product is a pain to deal for users that are passing single elements since they have to write Tuple1(1). Maybe this is a small issue, but a major selling point of Scala is more typing with less typing. But in this case it seems it's more typing with more typing. Please tell me: 1) I've missed this and it exists in another form, or 2) It will be added to a future version of the language (and

I have a piece of code as below: tupvalue = [('html', 96), ('css', 115), ('map', 82)] So while printing the above tuple in the desired format for a particular index I found a code like this: >>> '%s:%d' % tupvalue[0] 'html:96' I'm wondering how the single value tupvalue[0] is recognised as a tuple of two values by the format specifier '%s:%d' ? Please explain this mechanism with a documentation reference. How can I use a comprehension to format all the values in tupvalue in the required format as in the example shown? First, the easy question: How can I use a comprehension to format all the