First of all, a tuple is quick and easy: instead of writing a class for every time you want to put 2 things together, there’s a template that does it for you. Second of all, they’re generic. For example, in C++ the std::map uses an std::pair of key and value. Thus ANY pair can be … Read more
What prevents the language from having the special construct you want is its design. The designers just didn’t put this in, because it would complicate the language definition, which is quite minimalistic. fst and snd are library functions for the common case of pairs; you can define all the others yourself, or better, define record … Read more
Works with any tuple (scala 2.8): myTuple.productIterator.toList Scala 2.7: (0 to (myTuple.productArity-1)).map(myTuple.productElement(_)).toList Not sure how to maintain type info for a general Product or Tuple, but for Tuple2: def tuple2ToList[T](t: (T,T)): List[T] = List(t._1, t._2) You could, of course, define similar type-safe conversions for all the Tuples (up to 22).
std::tie makes non-const references. auto ref_tuple = std::tie(a,b); // decltype(ref_tuple) == std::tuple<int&, int&> For const references, you’ll either want the std::cref wrapper function: auto cref_tuple = std::make_tuple(std::cref(a), std::cref(b)); Or use a simply as_const helper to qualify the variables before passing them off to std::tie: template<class T> T const& as_const(T& v){ return v; } auto cref_tuple … Read more
It was pointed out in the comments under the question, but I’d like to clearly state that there is a method for that very same purpose: mutating func formUnion<S>(_ other: S) where Element == S.Element, S : Sequence Usage: var attendees: Set = [“Alicia”, “Bethany”, “Diana”] let visitors = [“Diana”, “Marcia”, “Nathaniel”] attendees.formUnion(visitors) print(attendees) // … Read more
In modern versions of Python I’d suggest what SilentGhost posted (repeating here for clarity): sum(i for i, j in list_of_pairs) In an earlier version of this answer I had suggested this, which was necessary because SilentGhost’s version didn’t work in the version of Python (2.3) that was current at the time: sum([pair[0] for pair in … Read more
You can do this: import csv # note: If you use ‘b’ for the mode, you will get a TypeError # under Python3. You can just use ‘w’ for Python 3 data=[(‘smith, bob’,2),(‘carol’,3),(‘ted’,4),(‘alice’,5)] with open(‘ur file.csv’,’wb’) as out: csv_out=csv.writer(out) csv_out.writerow([‘name’,’num’]) for row in data: csv_out.writerow(row) # You can also do csv_out.writerows(data) instead of the for … Read more
As DSM mentions, tuple‘s are immutable, but even for lists, a more elegant solution is to use filter: tupleX = filter(str.isdigit, tupleX) or, if condition is not a function, use a comprehension: tupleX = [x for x in tupleX if x > 5] if you really need tupleX to be a tuple, use a generator … Read more
shape is just an attribute, not a method. Just use y_pred.shape (no parentheses). (The error message isn’t telling you that y_pred is a tuple, it’s telling you that y_pred.shape is a tuple.)
It is an easy way to return multiple values from a function; std::tuple<int,int> fun(); The result values can be used elegantly as follows: int a; int b; std::tie(a,b)=fun();