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Optional argument presence test
- To: bug-lisp at MIT-MC, bug-lispm at MIT-AI
- Subject: Optional argument presence test
- From: Guy Steele <GLS at SU-AI>
- Date: Wed, 11 Jul 79 00:18:00 GMT
- Original-date: 10 Jul 1979 1718-PDT
I too rather like the syntax &OPTIONAL (var1 init1 predvar1) (var2 init2 predvar2).
It does present certain implementational difficulties, but I think they can be
overcome. An interesting phenomenon is that if i<j (resp. i>j) and predvari
is null (resp. non-null) then predvarj is also. Compiler optimizers take note!