car, cdr, and others
car, cdr, and others — return specific elements of a list.
Syntax
car (list)
cdr (list)
caar (list)
cadr (list)
cdar (list)
cddr (list)
caaar (list)
caadr (list)
cadar (list)
caddr (list)
cdaar (list)
cdadr (list)
cddar (list)
cdddr (list)
Returns
An element of the list or nil.
Description
The car function returns the first element
of a list. The cdr function returns all of
the list except for the first element. The remaining functions
in this group are simply shortcuts for the common combinations
of car and cdr. The
shortcut functions are read from left to right as nested
car and cdr calls.
Thus, a call to caddr (mylist) would be
equivalent to car (cdr
(cdr (mylist))). If the argument is not a
list, the result is nil. The
cdr function will only return a non-list
result in the case of a dotted pair.
Example
Gamma> car(list(1,2));
1
Gamma> cdr(list(1,2));
(2)
Gamma> cdr(cons(1,2));
2
Gamma> caadr (list (1, list(2, 3, list(4, 5), 6)));
2
Gamma> cdadr (list (1, list(2, 3, list(4, 5), 6)));
(3 (4 5) 6)
Gamma>
