setqand sequencing is specified by the special operator
setq, which looks like this:
The expression is evaluated and identifier is updated
with the result. The result of the
setq expression is the value
of expression. Here are some examples:
4... not a good idea in general! We can also try to update
nil, however, this is not permitted.
prognand is equivalent to Pascal's
}. It looks like this:
(progn exp-1 ...
Each of the expressions exp-1 to exp-n is evaluated
in order. The result of
The most common occurrence of
progn is in the consequent
or alternative branches of an
if expression. Note that it is
not needed in
cond expressions, since the consequent in each
case, can be a sequence of expressions.