I will suggest an analogy to a similar (but simpler) situation.
Suppose you are adding up some numbers.
foo = let { x = 3; y = 4; z = 5 } in x + y + z
That pattern only works if you know in advance how many numbers you are
going to add.
Otherwise, you need a function that works on a whole list of numbers:
sum = foldr (+) 0
So...the short answer to your question is: use recursion. The better answer
is: use library functions that do the recursion for you. You might want to
look at foldM:
http://hackage.haskell.org/packages/archive/base/latest/doc/html/Control-Monad.html#v:foldM
-Karl
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
