in reply to Re^3: How am i doing?
in thread How am i doing?

ChatGPT agrees, HOW CAN I BE WRONG? ;-P

<Reveal this spoiler or all in this thread>

Yes I'm sure, because I've seen it multiple times used this way, IIRC also in HOP.

The F(n) = F(n-1) + F(n-2) for n > 1 part is straightforwardly implemented with recursion.

> implementing the Fibonacci sequence by recursion is very ineffective.

(Slightly nitpicking) It's inefficient but effective!

The point is you get a correct result, even if you waste processing power.

The "memoisation" you mentioned solves this efficiency problem of needlessly recalculating known results.

IOW, the schoolbook continues evolving the example to deeper depth (sic).

Keep in mind that the classic MIT lectures on programming used to be in Lisp and original Lisp didn't have loops, only those "tail recursions".

Cheers Rolf
(addicted to the Perl Programming Language :)
see Wikisyntax for the Monastery

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Re^5: How am i doing?
by hippo (Archbishop) on Jul 21, 2025 at 10:38 UTC

    Yes, you do recall correctly. From section 1.8 of HOP (page 33 in my version):

    Sometimes a problem appears to be naturally recursive, and then the recursive solution is grossly inefficient. A very simple example arises when you want to compute Fibonacci numbers. This is a rather unrealistic example, but it has the benefit of being very simple.

    🦛

[reply]
      > Keep in mind that the classic MIT lectures on programming used to be in Lisp and original Lisp didn't have loops, only those "tail recursions".

      I know pretty well, and that's not just Lisp. At $job-2, we had a significant codebase in Erlang, which doesn't have loops, either.

      map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]
        IIRC Fibonacci was also heavily used to show the advantages of Haskell in one of the canonical books.

        But unfortunately I never went thru learning Haskell.

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        see Wikisyntax for the Monastery

[reply]

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