• subsetp list-1 list-2 &key key test test-not → generalized-boolean

• list-1 - a proper list.
• list-2 - a proper list.
• test - a designator for a function of two arguments that returns a generalized boolean.
• test-not - a designator for a function of two arguments that returns a generalized boolean.
• key - a designator for a function of one argument, or nil.
• generalized-boolean - a generalized boolean.

subsetp returns true if every element of list-1 matches some element of list-2, and false otherwise.

Whether a list element is the same as another list element is determined by the functions specified by the keyword arguments. The first argument to the :test or :test-not function is typically part of an element of list-1 extracted by the :key function; the second argument is typically part of an element of list-2 extracted by the :key function.

The argument to the :key function is an element of either list-1 or list-2; the return value is part of the element of the supplied list element. If :key is not supplied or nil, the list-1 or list-2 element itself is supplied to the :test or :test-not function.

(defparameter *cosmos* '(1 "a" (1 2))) 

→

*COSMOS*



(subsetp '(1) *cosmos*) 

→

true



(subsetp '((1 2)) *cosmos*) → false
(subsetp '((1 2)) *cosmos* :test #'equal) 

→

true



(subsetp '(1 "A") *cosmos* :test #'equalp) 

→

true



(subsetp '((1) (2)) '((1) (2))) 

→

false



(subsetp '((1) (2)) '((1) (2)) :key #'car) 

→

true

None.

None.

Should be prepared to signal an error of type type-error if list-1 and list-2 are not proper lists.

{\secref\TraversalRules}

To be done.

The :test-not parameter is deprecated.

\issue{MAPPING-DESTRUCTIVE-INTERACTION:EXPLICITLY-VAGUE} \issue{TEST-NOT-IF-NOT:FLUSH-ALL}