There are cases where the same algorithm will optimize better in a pure context. Specifically, stream fusion allows an algorithm that consists of a sequence of loops that may be of widely varying form: maps, filters, folds, unfolds, to be composed into a single loop. The equivalent optimization in a conventional imperative setting, with mutable … Read more
The great thing about clojure is you can attach the reporting to the data itself instead of the code that does the computing. This allows you to separate these logically distinct parts. Here is a chunk from my misc.clj that I find I use in just about every project: (defn seq-counter “calls callback after every … Read more
Javascript: OO and functional.
Haskell isn’t as hard as people like to make out to learn. Haskell opens up a new world that you never knew existed for you. It’s as valuable to learn as any other language. You might not find a job requiring you to do Haskell programming, but does that really mean a language isn’t valuable? … Read more
TL;DR A functional implementation can be faster than your original procedural implementation, in certain cases. Why is the functional style so much slower than the imperative style? Is there some problem with the functional implementation which is causing such a huge slowdown? As Matthieu M. already pointed out, the important thing to note is that … Read more
Your example of declarative programming above is not an actual program, so it’s not a good example. The main difference is between imperative and declarative. Functional is a particular kind of declarative. C, C++, Java, Javascript, BASIC, Python, Ruby, and most other programming languages are imperative. As a rule, if it has explicit loops (for, … Read more
I consider it a half-truth. Haskell has an amazing ability to abstract, and that includes abstraction over imperative ideas. For example, Haskell has no built-in imperative while loop, but we can just write it and now it does: while :: (Monad m) => m Bool -> m () -> m () while cond action = … Read more
A great C# example of declarative vs. imperative programming is LINQ. With imperative programming, you tell the compiler what you want to happen, step by step. For example, let’s start with this collection, and choose the odd numbers: List<int> collection = new List<int> { 1, 2, 3, 4, 5 }; With imperative programming, we’d step … Read more