Wolfgang Lux wrote:

>   let myfunc l =
>     let g y result =
>           if ypred y then
>             let z = verbose_code_using_y y in z_expression :: result
>           else
>             result
>     in let f x result =
>          if xpred x then
>            let y = verbose_code_using_x x in g y result
>          else
>            result
>     in fold_right f l []

Just correcting myself. The code should use fold_left rather than 
fold_right
(and thus switch the parameters in the call as well as that of the local
functions f and g) because the former is tail recursive and therefore 
should
be preferred in a strict language (have been programming too much 
Haskell
lately where a right fold is better).

Wolfghang