[Haskell] recursion patterns?

[Henning Thielemann]

On Wed, 15 May 2013, 7stud wrote:

> Well, my question does not meet the standards for a question at stackoverflow:
>
> (I am a haskell beginner)

Then you might want to post your question to haskell-beginners mailing 
list.

> Is one solution more efficient than the other?  I believe my solution is 
> tail recursive, but it's my understanding that compilers can now 
> optimize just about anything into tail recursion.

The first solution works for infinite lists and the second one does not. 
It's really like foldr vs. foldl.