I have to admit I understand Haskell a lot less than I thought I did (which wasn't much to begin with -- I've done maybe four or five Euler Project puzzles with

I have to admit I understand Haskell a lot less than I thought I did (which wasn't much to begin with -- I've done maybe four or five Euler Project puzzles with it and nothing else). I tried this same Fibonacci function on my machine using GHC 6.8.1, and it's clearly O(1.62^N). I withdraw my earlier dumb statement.