Henning Thielemann writes:
Caching is not the default, but you can easily code this by yourself: Define an array and initialize it with all function values. Because of lazy evaluation the function values are computed only when they are requested and then they persist in the array. One should add this most simple case to the Wiki.
A posteriori thought, when I reread that... This is a =part= of the story. Whatever you do with the initial calls, if there is no automatic memoization, further calls will be executed normally. The user has to replace his/her calls with the elements of the memo-array. Suppose (sorry for the awful Fibonacci again...) we define fibs = [fib n | n<-[0 ..]] fib 0 = 0 fib 1 = 1 fib n = fib(n-1) + fib(n-2) If you try to get fibs!!1000 you will die before anyway. The solution is obviously to replace the recursive definition of fib by fib n = fibs!!(n-1) + fibs!!(n-2) This works well. I had a similar problem in physics, perturbation theory offers often some quite intricate, knotty recurrencies, and the memoization offers a solution for the worse than exponential complexity. But I had to use trees, 2_dim lists of lists, etc. in order to sort the order of the creation of the results appropriately. So, I agree wholeheartly with the statement that memoization is not a blind automaton, it should be used consciously, and adapted to concrete needs. Jerzy Karczmarczuk