🚀 go-pugleaf

From article <7476@mentor.cc.purdue.edu>, by ksb@mentor.cc.purdue.edu (Kevin Braunsdorf):

...
> 
> What I did was much simpler than most of the systems I saw described at
> the time.  I simply made `cons' defer evaluation of its arguments until
> either `car' or `cdr' was called on the resulting CONSBOX (which was
> tagged as being LAZY, and had a saved environment hung on it).

Just for the record, what you did is not full lazy evaluation. But
as I noted earlier, defering the evaluation of a CONS is probably
the most important 'lazy deferal' for practical purposes.

There's a book that explains an implementation of lazy evaluation
pretty well, called _Functional Programming, Application and Implementation_,
by Peter Henderson, Prentice-Hall 1980. I don't know if it's still in
print or not.