Memoization
Imagine you have a long running function that you’d like to avoid running unnecessarily. For the purposes of this post you’ll have to suspend disbelief and pretend that negating a number is an expensive task. This example prints out a message so you can see when it actually gets called. let Negate n = printfn "Negating '%A' this is hard work" n -n val Negate : int -> int > Negate 5;; Negating '5' this is hard work val it : int = -5 Now, let’s use that function when writing another.