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Re: Implementation of MAP, SOME, EVERY, etc...
- To: Rob MacLachlan <RAM@CMU-CS-C.ARPA>, common-lisp@SU-AI.ARPA
- Subject: Re: Implementation of MAP, SOME, EVERY, etc...
- From: Dave Dyer <DDYER@USC-ISIB.ARPA>
- Date: Thu, 21 Mar 1985 00:07:00 -0000
- In-reply-to: <RAM.12096483296.BABYL@CMU-CS-C.ARPA>
I disagree with RAM; Imposing the requirement that all lists
passed to MAPxxx be "proper" imposes an unnecesary burden on
the use of mapping functions; The programmer shouldn't have to
know anything about the lists passed to MAPxxx except that the
sortest list is a proper list.
Besides, it would be an extremely poor implementation technique
to take LENGTH of all the lists before starting work -- I would say
that system functions should NEVER use LENGTH unless it is otherwise
known that the functin in question will inspect every element of the
list anyway, both because lists might legitimately be "improper",
and because lists can legitimately be very long, which makes