[Haskell-cafe] Re: Understanding tail recursion and trees

Edsko de Vries devriese at cs.tcd.ie
Thu May 1 08:32:37 EDT 2008


Thanks to Miguel for pointing out my silly error. So at least my
understanding of tail recursion is correct :) So then the question
becomes: what *is* the best way to write this function? One version I
can think of is

> ecount :: [Tree] -> Integer -> Integer
> ecount []                  acc = acc
> ecount (Leaf _       : ts) acc = ecount ts $! (acc + 1)
> ecount (Branch t1 t2 : ts) acc = ecount (t1 : t2 : ts) acc

which essentially maintains an explicit stack and runs on all trees. Are
there better ways to do this?

Thanks again and sorry for my mistake,


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