Let me answer this with a question: Which output do you expect for: main = print $ fmap (*2) (“funny”,2) You can have something as you want (using data Pair a = Pair a a or so), but as (,) may have different types in their first and second argument, you are out of luck.
Use the builtin function zip(): In Python 3: z = list(zip(x,y)) In Python 2: z = zip(x,y)
Question: Why doesn’t the same piecewise constructibility exist for arrays and tuples? My recollection is that piecewise construction was added to std::pair for one reason only: to support uses-allocator construction of the pair elements, i.e. to allow an allocator to be provided and conditionally passed to the elements if they support construction with an allocator … Read more
def foo : (Int, String, String) = (1, “Hello”, “World”) The compiler will interpret the type (Int, String, String) as a Tuple3[Int, String, String]
I think this is a subtle implementation of a Monad-like thing, specifically something in the same spirit of the continuation monad. Monads are a functional programming construction used to simulate state between different steps of a computation (Remember that a functional language is stateless). What a monad does is to chain different functions, creating a … Read more
Generally, you can use the func(*tuple) syntax. You can even pass a part of the tuple, which seems like what you’re trying to do here: t = (2010, 10, 2, 11, 4, 0, 2, 41, 0) dt = datetime.datetime(*t[0:7]) This is called unpacking a tuple, and can be used for other iterables (such as lists) … Read more
There’s a good article on the topic in the Python wiki: Why Lists Can’t Be Dictionary Keys. As explained there: What would go wrong if Python allowed using lists as keys, say, using their memory location as the hash? It would cause some unexpected behavior. Lists are generally treated as if their value was derived … Read more
why is a tuple converted to a string when it only contains a single string? a = [(‘a’), (‘b’), (‘c’, ‘d’)] Because those first two elements aren’t tuples; they’re just strings. The parenthesis don’t automatically make them tuples. You have to add a comma after the string to indicate to python that it should be … Read more
It is the commas, not the parentheses, which are significant. The Python tutorial says: A tuple consists of a number of values separated by commas Parentheses are used for disambiguation in other places where commas are used, for example, enabling you to nest or enter a tuple as part of an argument list. See the … Read more
In general, the element types of a tuple aren’t the same, so map doesn’t make sense. You can define a function to handle the special case, though: scala> def map[A, B](as: (A, A))(f: A => B) = as match { case (a1, a2) => (f(a1), f(a2)) } map: [A,B](as: (A, A))(f: (A) => B)(B, B) … Read more