Function FIND-VARIABLE-VALUE

Package:

COMMON-LISP.EXTENSIONS.DATA-AND-CONTROL-FLOW.UNIFICATION

Syntax:

  find-variable-value variable-name &optional env errorp
  => value, found
  

  v? variable-name env &optional plain-symbol-p
  => value, found
  

Arguments and Values:

variable-name : a symbol denoting a unification variable

plain-symbol-p : a boolean

env : a unification-environment

value : an object

found : a boolean

Description:

The function FIND-VARIABLE-VALUE searches the environment env for the value associated to the unification variable variable-name.

If there is a value associated to variable-name in env, then it is returned; found, the second return value, is T.

If no value is associated to variable-name then FIND-VARIABLE-NAME signals an error of type UNIFICATION-VARIABLE-UNBOUND if errorp is non-NIL (the default.) If errorp is NIL then FIND-VARIABLE-NAME returns the values NIL and NIL.

env defaults to *NULL-ENVIRONMENT*.

The V? function is a utility to be used for debugging purposes at the listener. The optional argument plain-symbol-p can be used to avoid using the '?' syntax for variables.

Affected By:

None.

Exceptional Situations:

None.

See Also:

UNIFY:ENVIRONMENT, BINDING, UNIFICATION-VARIABLE-UNBOUND, *NULL-ENVIRONMENT*

Notes:

None.