It is sometimes useful to make two variables synonyms, so that both
variables always have the same value, and changing either one also
changes the other. Whenever you change the name of a
variable—either because you realize its old name was not well
chosen, or because its meaning has partly changed—it can be useful
to keep the old name as an alias of the new one for
compatibility. You can do this with
defvaraliasnew-alias base-variable &optional docstring
This function defines the symbol new-alias as a variable alias for symbol base-variable. This means that retrieving the value of new-alias returns the value of base-variable, and changing the value of new-alias changes the value of base-variable. The two aliased variable names always share the same value and the same bindings.
If the docstring argument is non-
nil, it specifies the
documentation for new-alias; otherwise, the alias gets the same
documentation as base-variable has, if any, unless
base-variable is itself an alias, in which case new-alias gets
the documentation of the variable at the end of the chain of aliases.
This function returns base-variable.
Variable aliases are convenient for replacing an old name for a
variable with a new name.
make-obsolete-variable declares that
the old name is obsolete and therefore that it may be removed at some
stage in the future.
make-obsolete-variableobsolete-name current-name when &optional access-type
This function makes the byte compiler warn that the variable obsolete-name is obsolete. If current-name is a symbol, it is the variable’s new name; then the warning message says to use current-name instead of obsolete-name. If current-name is a string, this is the message and there is no replacement variable. when should be a string indicating when the variable was first made obsolete (usually a version number string).
The optional argument access-type, if non-
specify the kind of access that will trigger obsolescence warnings; it
can be either
You can make two variables synonyms and declare one obsolete at the
same time using the macro
define-obsolete-variable-aliasobsolete-name current-name &optional when docstring
This macro marks the variable obsolete-name as obsolete and also makes it an alias for the variable current-name. It is equivalent to the following:
(defvaralias obsolete-name current-name docstring) (make-obsolete-variable obsolete-name current-name when)
This function returns the variable at the end of the chain of aliases of variable. If variable is not a symbol, or if variable is not defined as an alias, the function returns variable.
This function signals a
cyclic-variable-indirection error if
there is a loop in the chain of symbols.
(defvaralias 'foo 'bar) (indirect-variable 'foo) ⇒ bar (indirect-variable 'bar) ⇒ bar (setq bar 2) bar ⇒ 2
foo ⇒ 2
(setq foo 0) bar ⇒ 0 foo ⇒ 0