[Haskell-cafe] Simple list processing

[Henning Thielemann]

On Wed, 11 Jun 2008, Thomas M. DuBuisson wrote:

> Why is there no mapAccumL' (strict)?  Just a library deficiency that we
> can remedy or am I missing something?

The strictness in foldl' is needed to avoid that unevaluated computations 
accumulate until the end of the list. In mapAccumL and scanl this danger 
is smaller. If you process the elements of the output list in order then 
the intermediate states are also computed step by step. However, if you 
evaluate only the last element of the output list you have the same 
problem like with foldl.