The following functions can be used to access symbol properties.
This function returns the value of the property named property in symbol's property list. If there is no such property, it returns
nil. Thus, there is no distinction between a value of
niland the absence of the property.
The name property is compared with the existing property names using
eq, so any object is a legitimate property.
putfor an example.
This function puts value onto symbol's property list under the property name property, replacing any previous property value. The
putfunction returns value.(put 'fly 'verb 'transitive) ⇒'transitive (put 'fly 'noun '(a buzzing little bug)) ⇒ (a buzzing little bug) (get 'fly 'verb) ⇒ transitive (symbol-plist 'fly) ⇒ (verb transitive noun (a buzzing little bug))
This function sets symbol's property list to plist. Normally, plist should be a well-formed property list, but this is not enforced. The return value is plist.(setplist 'foo '(a 1 b (2 3) c nil)) ⇒ (a 1 b (2 3) c nil) (symbol-plist 'foo) ⇒ (a 1 b (2 3) c nil)
For symbols in special obarrays, which are not used for ordinary purposes, it may make sense to use the property list cell in a nonstandard fashion; in fact, the abbrev mechanism does so (see Abbrevs).
You could define
putin terms of
plist-put, as follows:(defun put (symbol prop value) (setplist symbol (plist-put (symbol-plist symbol) prop value)))
This function is identical to
get, except that if symbol is the name of a function alias, it looks in the property list of the symbol naming the actual function. See Defining Functions. If the optional argument autoload is non-
nil, and symbol is auto-loaded, this function will try to autoload it, since autoloading might set property of symbol. If autoload is the symbol
macro, only try autoloading if symbol is an auto-loaded macro.