I'm attaching a reference implementation that works.

This solves the following problems  (in order of importance) with
the past reference implementation:

1. Problems with (force  (lazy (delay expr))).  See  my mail with
   Message-Id 20040611070831.GA29954@bachue.com for details.

2. Fixes stream-filter.  The previous  version wouldn't work when
   passed stream-null (as in (stream-filter even? stream-null)).

3. Changes the name make-stream to ##srfi-40#make-stream as it is
   a rather  low-level operation and  it /might/ be  desirable to
   define make-stream with an interface similar to make-list.

I hope it helps.

Alejo.
http://bachue.com/alejo

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