Lists in Lisp are not a primitive data type; they are built up from
@dfn{cons cells}. A cons cell is a data object that represents an
-ordered pair. It records two Lisp objects, one labeled as the @sc{car},
-and the other labeled as the @sc{cdr}. These names are traditional; see
-@ref{Cons Cell Type}. @sc{cdr} is pronounced ``could-er.''
+ordered pair. It holds, or ``points to,'' two Lisp objects, one labeled
+as the @sc{car}, and the other labeled as the @sc{cdr}. These names are
+traditional; see @ref{Cons Cell Type}. @sc{cdr} is pronounced
+``could-er.''
A list is a series of cons cells chained together, one cons cell per
element of the list. By convention, the @sc{car}s of the cons cells are
Each pair of boxes represents a cons cell. Each box ``refers to'',
``points to'' or ``contains'' a Lisp object. (These terms are
-synonymous.) The first box, which is the @sc{car} of the first cons
-cell, contains the symbol @code{tulip}. The arrow from the @sc{cdr} of
-the first cons cell to the second cons cell indicates that the @sc{cdr}
-of the first cons cell points to the second cons cell.
+synonymous.) The first box, which describes the @sc{car} of the first
+cons cell, contains the symbol @code{tulip}. The arrow from the
+@sc{cdr} box of the first cons cell to the second cons cell indicates
+that the @sc{cdr} of the first cons cell is the second cons cell.
The same list can be illustrated in a different sort of box notation
like this:
@defun setcar cons object
This function stores @var{object} as the new @sc{car} of @var{cons},
-replacing its previous @sc{car}. It returns the value @var{object}.
-For example:
+replacing its previous @sc{car}. In other words, it changes the
+@sc{car} slot of @var{cons} to point to @var{object}. It returns the
+value @var{object}. For example:
@example
@group
@defun setcdr cons object
This function stores @var{object} as the new @sc{cdr} of @var{cons},
-replacing its previous @sc{cdr}. It returns the value @var{object}.
+replacing its previous @sc{cdr}. In other words, it changes the
+@sc{cdr} slot of @var{cons} to point to @var{object}. It returns the
+value @var{object}.
@end defun
Here is an example of replacing the @sc{cdr} of a list with a
You can delete elements from the middle of a list by altering the
@sc{cdr}s of the cons cells in the list. For example, here we delete
the second element, @code{b}, from the list @code{(a b c)}, by changing
-the @sc{cdr} of the first cell:
+the @sc{cdr} of the first cons cell:
@example
@group
This function reverses the order of the elements of @var{list}.
Unlike @code{reverse}, @code{nreverse} alters its argument by reversing
the @sc{cdr}s in the cons cells forming the list. The cons cell that
-used to be the last one in @var{list} becomes the first cell of the
+used to be the last one in @var{list} becomes the first cons cell of the
value.
For example:
@result{} (4 3 2 1)
@end group
@group
-;; @r{The cell that was first is now last.}
+;; @r{The cons cell that was first is now last.}
x
@result{} (1)
@end group
An @dfn{association list}, or @dfn{alist} for short, records a mapping
from keys to values. It is a list of cons cells called
-@dfn{associations}: the @sc{car} of each cell is the @dfn{key}, and the
+@dfn{associations}: the @sc{car} of each cons cell is the @dfn{key}, and the
@sc{cdr} is the @dfn{associated value}.@footnote{This usage of ``key''
is not related to the term ``key sequence''; it means a value used to
look up an item in a table. In this case, the table is the alist, and