higher-order-functions

There are quite a few blog posts (like this ) on usages of the standard library functions apply / with / run / also / let available that make it a bit easier to distingish when to actually use which of those pretty functions. For a few weeks now, the official docs even provide guidelines on that topic finally: https://kotlinlang.org/docs/reference/coding-conventions.html#using-scope-functions-applywithrunalsolet Nevertheless, I think it is pretty hard to memorize the function's individual use cases by the function names . I mean, for me they seem to be interchangeable, why isn't let called run

While going through Functional Programming in Scala , I came across this question: Can you right foldLeft in terms of foldRight? How about the other way around? In solution provided by the authors they have provided an implementation as follows: def foldRightViaFoldLeft_1[A,B](l: List[A], z: B)(f: (A,B) => B): B = foldLeft(l, (b:B) => b)((g,a) => b => g(f(a,b)))(z) def foldLeftViaFoldRight[A,B](l: List[A], z: B)(f: (B,A) => B): B = foldRight(l, (b:B) => b)((a,g) => b => g(f(b,a)))(z) Can somebody help me trace through this solution and make me understand how this actually gets the foldl

I'm currently doing a Functional Programming course and I'm quite amused by the concept of higher-order functions and functions as first class citizens. However, I can't yet think of many practically useful, conceptually amazing, or just plain interesting higher-order functions. (Besides the typical and rather dull map , filter , etc functions). Do you know examples of such interesting functions? Maybe functions that return functions, functions that return lists of functions (?), etc. I'd appreciate examples in Haskell, which is the language I'm currently learning :) Well, you notice that

Haskell (with the GHC compiler) is a lot faster than you'd expect . Used correctly, it can get close-ish to low-level languages. (A favorite thing for Haskellers to do is to try and get within 5% of C (or even beat it, but that means you are using an inefficient C program, since GHC compiles Haskell to C).) My question is, why? Haskell is declarative and based on lambda calculus. Machine architectures are clearly imperative, being based on turing machines, roughly. Indeed, Haskell doesn't even have a specific evaluation order. Also, instead of dealing with machine data types, you make

I'm studying higher order functions following the Eloquent JavaScript book. I haven't been able to understand this code, why is "Boolean" passed as noisy first argument? This is supposed to be function that changes other function, I just don't get how it works! function noisy(f) { return function(arg) { console.log("calling with", arg); var val = f(arg); console.log("called with", arg, "- got", val); return val; }; } noisy(Boolean)(0); // → calling with 0 // → called with 0 - got false noisy accepts any one-argument function as its argument. It returns a new function that calls that function,

def tracer(fn): def traced(x): print('Calling',fn,'(',x,')') result=fn(x) print('Got',result,'from',fn,'(',x,')') return result return traced def fact(n): if n ==0: return 1 return n * fact(n-1) new_fact = tracer(fact) new_fact(2) I used this code on pythontutor.com to better understand higher order functions, but i'm having difficulty understanding why new_fact(2) in step 8 is mapped to traced? In other words, how does the traced function know the argument is 2? In Python, functions are objects too. When you call the tracer() function, it returns the nested traced() function; it is in fact

Map value the particular key wherever presents in array of dictionary and replace it in same array. We need to update pan_card key 0 to 1 , in occurence of array of dictionary. let keyToUpdate = "pan_card" var arrayOfDictionary = [[String:Any]]() var firstDict = [String:Any]() firstDict["passport"] = 0 firstDict["ration_card"] = 0 firstDict["pan_card"] = 0 var arrayDict = [String : Any]() arrayDict["currentObject"] = firstDict arrayDict["title"] = "Documents list" var secondDict = [String:Any]() secondDict["dl"] = 0 secondDict["voter"] = 0 secondDict["pan_card"] = 0 //let dic = secondDict