Comments on: Fab Fib

By: the-free-energy

the-free-energy — Tue, 01 Dec 2009 12:15:10 +0000

Omg, I must say this is truly owning… Thanks for giving such a nice read, you made my day.

By: Eli

Eli — Wed, 11 Mar 2009 02:35:38 +0000

Trevor,

While that function works and is O(n), the Haskell example can generate all Integer (bignum) values in the fibonacci sequence, limited only by system RAM.

By: Trevor Bernard

Trevor Bernard — Mon, 24 Mar 2008 16:28:38 +0000

The Haskell implementation is just a little dynamic programming. It can easily but not quite as elegantly be done in any procedural language.

int fib[50];
fib[0] = 0;
fib[1] = 1;
for(int i=2; i<50; i++) {
fib[i] = fib[i-2] + fib[i-1];
}

By: russ

russ — Sun, 27 Jan 2008 17:11:09 +0000

Hi Scott, fancy seeing you here! No worries about the error – it’s surprisingly common to see the base cases mistyped in Fibonacci generators. In fact, the Haskell solution I discuss here actually had a similar mistake in the comment on your post, starting the list with 1 : 1 rather than 0 : 1 – strictly speaking, the sequence should start with 0. Keep up the good work with the Weekly Source Code, it’s an excellent series and very useful too.

By: russ

russ — Sun, 27 Jan 2008 17:04:54 +0000

Hi Don, thanks for the link! The parallel implementations are interesting, though they seem to me to be more an exercise in demonstrating Haskell’s parallel capabilities since they stick to the naive recursive approach. What I love about the zipWith solution is how it performs so well whilst retaining most of the elegance of the naive recursive solution.

By: Scott Hanselman

Scott Hanselman — Sat, 26 Jan 2008 18:43:17 +0000

It’s funny, I did a Haskell one in college and considered it for this post, but it was getting pretty long (the post) so I didn’t. Thanks for fixing my error and for a great writeup!

By: Don Stewart

Don Stewart — Sat, 26 Jan 2008 18:19:53 +0000

You might be interested in the collected Haskell fibonacci
implementations here: http://haskell.org/haskellwiki/The_Fibonacci_sequence
which includes neat, concise ones, and parallel ones that will use all
your cores.