I’m not interested in the first definition — those would not help me to write a real program (+1 if you convince me I’m wrong). Please help me understand the second definition. I think map, filter, and reduce are useful: they allow me to program at a higher level — fewer mistakes, shorter and clearer … Read more
I recommend cow-blog by Brian Carper. According to the author it was written with your purpose in mind.
I’ve done some research into this myself and thought I might add CONCURRENCY to the list of reasons to use a functional language. See at some point in the near future processor speed will not be able to increase using the same cpu technology. The physics of the architecture won’t allow it. So that is … Read more
You can have nested iterations in a single list comprehension: [filename for path in dirs for filename in os.listdir(path)] which is equivalent (at least functionally) to: filenames = [] for path in dirs: for filename in os.listdir(path): filenames.append(filename)
Since you explicitly asked for the most interesting and obscure ones: You can extend C-H to many interesting logics and formulations of logics to obtain a really wide variety of correspondences. Here I’ve tried to focus on some of the more interesting ones rather than on the obscure, plus a couple of fundamental ones that … Read more
I’ll answer this question incrementally. Let’s start with the = equivalence predicate. The = predicate is used to check whether two numbers are equal. If you supply it anything else but a number then it will raise an error: (= 2 3) => #f (= 2.5 2.5) => #t (= ‘() ‘()) => error The … Read more
In some cases, yes! There’s a beautiful paper called Bidirectionalization for Free! which discusses a few cases — when your function is sufficiently polymorphic — where it is possible, completely automatically to derive an inverse function. (It also discusses what makes the problem hard when the functions are not polymorphic.) What you get out in … Read more
The style of functional programming is to describe what you want, rather than how to get it. ie: instead of creating a for-loop with an iterator variable and marching through an array doing something to each cell, you’d say the equivalent of “this label refers to a version of this array where this function has … Read more
Yes, Swift has the Set class. let array1 = [“a”, “b”, “c”] let array2 = [“a”, “b”, “d”] let set1:Set<String> = Set(array1) let set2:Set<String> = Set(array2) Swift 3.0+ can do operations on sets as: firstSet.union(secondSet)// Union of two sets firstSet.intersection(secondSet)// Intersection of two sets firstSet.symmetricDifference(secondSet)// exclusiveOr Swift 2.0 can calculate on array arguments: set1.union(array2) // … Read more
Consider this: in all decent programming languages you can write functions, e.g. def f(arg) = result Here, f takes a value arg and computes a value result. It is a function from values to values. Now, some languages allow you to define polymorphic (aka generic) values: def empty<T> = new List<T>() Here, empty takes a … Read more