[Solved] How to write this function in point-free style?
Another solution (needs import of Control.Applicative): between min max = liftA2 (&&) (min <) (max >) 1 solved How to write this function in point-free style?
functional-programming
[Solved] Retrieving variables from functions
in javascript the IIFE and Closure principles var f = (function() { var localFunc = function(){}; var localVar1 = 3; var localVar2 = 4; // publish return { localFunc: localFunc, localVar: localVar1 } })(); f.localFunc(); // ok f.localVar2; // nok I don’t known if i answered the question solved Retrieving variables from functions
[Solved] why cannot javascript execute methods inside methods?
Because push returns the size of the array: The push() method adds new items to the end of an array, and returns the new length. It does execute the push function, it’s just not returning what you were expecting. JavaScript was written in only 10 days so we are stuck with some design decisions. It’s … Read more
[Solved] adding elements of a list in a given way in haskell [closed]
I think you’re looking for the inverse of this function conv = concat . f where f [] = [] f (x:xs) = map (x+) xs : f xs > conv [3,10,5] [13,8,15] > conv [2,5,15,34] [7,17,36,20,39,49] I came up something like this. Note that for length less than 3 there can’t be a unique … Read more
[Solved] What does this mean in Scala? [closed]
A few pieces of information that might help when looking at code like this: Calling an object or class as a function calls the appropriate apply method if there is one Parentheses are often optional so another way to rewrite the code above would be: val route = HttpService.apply({ case GET -> Root / “hello” … Read more
[Solved] Javascript can implement OOP but Ruby can’t implement functional programming? [closed]
Ruby does have first class functions. What makes you think it doesn’t? From wikipedia: A language that has first-class functions is one where: The language supports constructing new functions during the execution of a program, storing them in data structures, passing them as arguments to other functions, and returning them as the values of other … Read more
[Solved] Quick Union Functional Style [closed]
I think I got it. The solution was odd because it makes me wonder how does the original solution even worked. Basically I just rewrote the counter() in the parent class to return a array.distinct.length , i.e. the distinct integers or the roots: /* * takes the initial number of components * as its argument … Read more
[Solved] Advanced Rudimentary Computing? [closed]
I think you missed the most important one: algorithms. Understanding the complexity, know the situation to use them, why use them and more important, how to implement them. I’m pretty sure that you already know a lot about algorithms but if you think that your tool-knowledge (aka the programming languages) are good enough, you should … Read more
[Solved] OCaml: How can I return the first element of a list and after that remove it from the list?
I think there are a couple of misunderstandings here. First, most types in OCaml are immutable. Unless you use mutable variables you can’t “remove it from the list”, you can only return a version of the list that doesn’t have that first item. If you want to return both things you can achieve that using … Read more
[Solved] How to convert a list of string to map in Scala?
You can use List#grouped to create a non-overlapping window: list.grouped(2).map(l => (l(0), l(1))).toMap 7 solved How to convert a list of string to map in Scala?
[Solved] Higher order function parameter [closed]
Your call to and_ does not see director and “Brad Bird” directly; it gets the function that results from applying director to “Brad Bird” (and similarly for the second argument. and_ :: (Movie -> Bool) -> (Movie -> Bool) -> Movie -> Bool and_ f1 f2 (_, rank, dir) | … The bigger problem is … Read more
[Solved] How to find occurrences of char in an input string in Haskell
There are many ways to do this, but since you mention you’re a Haskell beginner, a list comprehension may be easiest to understand (I’m assuming this is homework, so you have to implement it yourself, not use elemIndices): stringCount str ch = [ y | (x, y) <- zip str [0..], x == ch ] … Read more
[Solved] Concat elements of tuple if contiguous lables are same
Here’s a quick function to do this looping through the tuples and comparing each tuple to the label of the previous tuple and concatenating them if the labels match. def parse_tuples(x): prev_tuple = list(x[0]) parsed = [] for i in x[1:]: if i[1] == prev_tuple[1]: prev_tuple[0] += i[0] else: parsed.append(tuple(prev_tuple)) prev_tuple = list(i) parsed.append(tuple(prev_tuple)) return … Read more
[Solved] Functional programming in JS
I’m assuming that you’re familiar with Haskell since you’re using Haskell idioms. You have the following functions: getLine :: () -> IO String — why isn’t this simply `getLine :: IO String`? cat :: String -> Task Error String The first thing you want to do is get rid of the superfluous function wrapping the … Read more
[Solved] How does “Stream” in java8 work?
abstract class ReferencePipeline<P_IN, P_OUT> extends AbstractPipeline<P_IN, P_OUT, Stream<P_OUT>> implements Stream<P_OUT> … It’s ReferencePipeline that implements them. For example: @Override public final boolean anyMatch(Predicate<? super P_OUT> predicate) { return evaluate(MatchOps.makeRef(predicate, MatchOps.MatchKind.ANY)); } 2 solved How does “Stream” in java8 work?