| IV. COND |
COND is an unusual function which may take any arbitrary number
of arguments. Each argument is called a clause, and consists of a list
of exactly two S-expressions. We will call the first S-expression in a clause
a condition, and the second S-expression a result. Thus, a call
to COND looks like this:
(COND
(condition1 result1 )
(condition2 result2 )
. . .
(T resultN ) )
The value returned by COND is computed as follows: if
condition1 is true (not NIL), then return
result1; else if condition2 is true then return
result2; else if ...; else return resultN. In most LISP
systems, it is an error if none of the conditions are true, and the
result of the COND is undefined. For this reason,
T is usually used as the final condition.
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