How to define this class in scala data NestedList a = Elem a | List [NestedList a] This in Haskell means a NestedList is a Type which can contain either Elem or another NestedList. Is it possible to do these kind of recursive definitions in scala? Actually this is what I am trying to acheive Check Problem 7 here in this page. Update...
I have a set of case classes like this abstract class Shape case class Rectangle(width: Int, height: Int) extends Shape case class Location(x: Int, y: Int, shape: Shape) extends Shape case class Circle(radius: Int) extends Shape case class Group(shape: Shape*) extends Shape where basically Group is an array of shapes. I need t...
Let's say I have an arbitray list of A class A { string K {get;set;} string V {get;set;} } ... List<A> theList = ... Is there an easy way to compose a dictionary from theList? (something like the following) Dictionary<string, string> dict = magic(x => x.K, x => x.V, theList) I don't want to write the following code: var d = new D...
It is a wonderful, very fast, mature and complete language. It exists for a very long time and has a big set of libraries. Yet, it appears not to be widely used. Why ? I suspect it is because it is pretty rough and unforgiving for beginners, and maybe because its lazy execution makes it even harder ...
I understand very clearly the difference between functional and imperative programming techniques. But there's a widespread tendency to talk of "functional languages", and this really confuses me. Of course some languages like Haskell are more hospitable to functional programming than other languages like C. But even the former does I/O...
What are some good examples that I can use to explain functional programming? The audience would be people with little programming experience, or people who only have object-oriented experience. ...
I'm guessing that there must be a better functional way of expressing the following: def foo(i: Any) : Int if (foo(a) < foo(b)) a else b So in this example f == foo and p == _ < _. There's bound to be some masterful cleverness in scalaz for this! I can see that using BooleanW I can write: p(f(a), f(b)).option(a).getOrElse(b) But ...
I work at an internet company and we make PHP and .Net (C #) sites / applications our principle is to get all colleagues to a higher level but also the efficiency is important there are 10 web developers and searching for the best mix to make applications like parallel programming / more developers one a project we also have used some...
I have a large array 15x15x2200. THis is merely a collection of 15x15 sparse matrices depicting the links between 15 nodes and how they vary over 2200 time units. I need to calculate for how much time does each link persist. By this I mean, suppose A[4,11] is 0 till time unit 5 and stays 1 till time unit 20 and then becomes 0 and again b...
Hi I am a newbie in functional programming. I just tried solving the following problem : [ a rough specification ] e.g.1: dividend : {3,5,9} divisor : {2,2} radix = 10 ans (remainder) : {7} Procedure : dividend = 3*10^2+5*10^1+9*10^0 = 359 similarly, divisor = 22 so 359 % 22 = 7 e.g.2: dividend : {555,555,555,555,555,555,555,555,55...
Is there a standard way of dealing with the interaction between separate compilation and different kinds of closure conversion when compiling higher-order function calls? I know of three function-like constructs that are distinctly compiled in most programming languages: closures, (top-level) functions, and C++-style function objects. S...
I'm sorry that I couldn't figure out a way to express the question more clearly in the headline, but essentially, it's this: almost all functional languages have constructs that allow you to process a variable list of arguments through tail recursion, as in this Erlang-ish pseudocode that sums up a list of numbers: sumup(0,A) -> A. sum...
I've noticed it seems to behave this way, but I don't want to rely on it if it's not intentional. Here's the code in question: let bestValuesUnder max = allValues >> List.partition (fun value -> value < max) >> function | ([], bad) -> [List.min bad] | (good, _) -> good // |> List.sortBy (fun value -> -value) ...
I am familiar with standard zipWith functions which operate on corresponding elements of two sequences, but in a functional language (or a language with some functional features), what is the most succinct way to conditionally select the pairs of elements to be zipped, based on a third sequence? This curiosity arose while scratching o...
I have a few restricted areas on the site, for which I would like to specify login_required decorator. However I would like to do that once per inclusion in main urls.py, not per individual url in included urls.py So instead of: /private/urls.py: (r'^profile/$', login_required(profile)), I'd do something along the lines: /urls.py ...
Hi, I was asked about one question I totally had no idea. What's the another name for function object in C++ 1) Actions 2) Predicates 3) Operators 4) Use case. I am confused about the point the question is supposed to deliver. I searched online a lot but no clue about that. ...
I searched in google to find the differences between the two, every one mentions that when you want to do pattern matching on the class use case class else use classes and also mentioning some extra perks like equals and hascode overriding. But are these the only reasons why one should use a case class instead of class? I guess there sho...
I have a hierarchically nested associative array. It looks like this: A = { B = { C = {}, D = {}, }, E = { F = { G = {} } }, H = {} } I would like to write a function that returns the "ancestors" of each key. So: f("A") = {"A"} f("B") = {"B","A"} f("C") =...
I am going to read the classic "Structure and Interpretation of Computer Programs" link text and it utilizes the Scheme language to teach its material. Does any one have advice about what Scheme would be easy to use (on Windows) and complete? Thanks! ...
Hi, I'm pretty new to Haskell and I'm trying to work out how to traverse a n-ary tree. As output I'm looking to get a list of Leaf values (as the branches have no value), so for testtree this would be: 4,5 My definition so far is: data Tree a = Leaf a | Branch [Tree a] deriving (Show) travTree :: Tree a -> [a] travT...