Automatic memoizing in functional programming languages

Question

I always thought that Haskell would do some sort of automatic intelligent memoizing. E.g., the naive Fibonacci implementation

fib 0 = 0
fib 1 = 1
fib n = fib         


        

Answer 1

For example of implementing automatic memoization, you may look at the Factor programming language and its Memoization vocabulary. For example, simple Fibonacci number generator:

: fib ( n -- n )
    dup 1 > [
        [ 1 - fib ]
        [ 2 - fib ]
        bi +
    ] when ;

may be memoized by replacing ":" word with "MEMO:"

MEMO: fib ( n -- n )
    dup 1 > [
        [ 1 - fib ]
        [ 2 - fib ]
        bi +
    ] when ;

In that case, fib inputs and corresponding outputs will be transparently stored within in-memory dictionary.

Factor language syntax may be confusing :). I recommend you to watch video presentation from Google Tech Talks about Factor to understand, how is it possible to implement memoization in that way.