rplaca, rplacd
rplaca, rplacd — replace the car and cdr of a list.
Syntax
rplaca (cons, s_exp)
rplacd (cons, s_exp)
Arguments
- list
- s_exp
Any Gamma or Lisp expression.
Returns
The s_exp, or nil on failure.
Description
These functions destructively alter the form of a
list. rplaca modifies the car of a list,
effectively replacing the first element.
rplacd modifies the cdr of a list,
replacing the entire tail of the list. These functions have no
meaning for non-lists. To entirely remove the tail of a list,
replace the cdr of the list with nil.
Example
Gamma> x = list(1,2,3,4);
(1 2 3 4)
Gamma> rplaca(x,0);
0
Gamma> x;
(0 2 3 4)
Gamma> rplacd(x,list(7,8,9,10,11,12));
(7 8 9 10 11 12)
Gamma> x;
(0 7 8 9 10 11 12)
Gamma>
