There are a number of other Lisp functions which you may want to 
review in your code which are rather cons-heavy and can be replaced
with non-consing function.  For example, if you don't need to use
the result of a mapcar function, then use do, dolist or times instead.
Also, reverse copies whereas delete doesn't (but be careful).  
String-manipulation functions like subseq, concatenate and format
cons heaviliy as well.  I've also discovered that (at least in Allegro
4.2), using closures can be cons-intensive and often replacable; for
example, any function such as some or every which takes a function
as an argument.

--Pete


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