How laziness changes thinking in Haskell

The example given in the article can be addressed by using foldl' instead of foldr. The issue is discussed in

http://www.haskell.org/haskellwiki/Foldr_Foldl_Foldl

A Haskell programmer needs to understand when non-strict evaluation can/should be avoided. foldr is usually more elegant but sometimes less efficient.

I've read a whole lot about Haskell, but still haven't fired up ghc for fear of spending too much time playing with it. This post makes me even more interesting to play with it, but even more scared that I will like it. I'm afraid that I will like it because I am afraid I will run into stuff like this when it is too late.

Unrelated comment: do any other Haskell fans know of a solution or debugging strategies for this problem?

There are a number of useful tips in this article about when, and how, to use strict evaluation in Haskell.

http://users.aber.ac.uk/afc/stricthaskell.html

"Ugh, I'm too tired to learn Haskell. Maybe another day."

That kind of laziness? (I kid, I kid, we all know it's "I'll learn Haskell only when I have to compute something which requires me to know it. I mean, I thunk I know it.")