Combinations of car and cdr

Since combinations of car and cdr are frequently used, all combinations up to four uses of car and cdr are defined as functions of the form cxxxr:

(caar x)    = (car (car x))

(cadr x) = (car (cdr x))

(caddr x) = (car (cdr (cdr x)))

Rule: The operations closer to the argument are done first.

It's worth memorizing some common combinations:

car = first element of a list


= second element


= third element


= fourth element

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