[Haskell-cafe] Writer + log each computation to stdout

[oleg at okmij.org]

> Extensible Effects designed specifically to separate a client (the
> requestor of an action) from a handler, the executor of an action. A
> logging client merely requests a string to be logged. It has no idea
> what happens when that request is executed. Therefore, the same
> client can be used with several handlers, even within the same
> expression.  One can also build various interceptors, such as
> logIntercept, which is similar to Unix' tee.
>
> The following file illustrates how to solve the problem with all three
> scenarios.
>         http://okmij.org/ftp/

I forgot to complete the link! I'm very sorry. Here is the correct
link to the code solving the posed problem:

        http://okmij.org/ftp/Haskell/extensible/WriterEx.hs