Commit 3998eed0 authored by Richard M. Stallman's avatar Richard M. Stallman

*** empty log message ***

parent 9b784e96
......@@ -32,17 +32,21 @@ the whole list.
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 holds, or ``refers 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
the elements of the list, and the @sc{cdr}s are used to chain the list:
the @sc{cdr} of each cons cell is the following cons cell. The @sc{cdr}
of the last cons cell is @code{nil}. This asymmetry between the
@sc{car} and the @sc{cdr} is entirely a matter of convention; at the
ordered pair. That is, it has two slots, and each slot @dfn{holds}, or
@dfn{refers to}, some Lisp object. One slot is known as the @sc{car},
and the other is known as the @sc{cdr}. (These names are traditional;
see @ref{Cons Cell Type}.) @sc{cdr} is pronounced ``could-er.''
We say that ``the @sc{car} of this cons cell is'' whatever object
its @sc{car} slot currently holds, and likewise for the @sc{cdr}.
A list is a series of cons cells ``chained together,'' so that each
cell refers to the next one. There one cons cell for each element of
the list. By convention, the @sc{car}s of the cons cells hold the
elements of the list, and the @sc{cdr}s are used to chain the list: the
@sc{cdr} slot of each cons cell refers to the following cons cell. The
@sc{cdr} of the last cons cell is @code{nil}. This asymmetry between
the @sc{car} and the @sc{cdr} is entirely a matter of convention; at the
level of cons cells, the @sc{car} and @sc{cdr} slots have the same
characteristics.
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