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Function SUBSETP

Syntax

  • subsetp list-1 list-2 &key key test test-notgeneralized-boolean

Arguments and Values

Description

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.

Examples

(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

Side Effects

None.

Affected By

None.

Exceptional Situations

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

See Also

{\secref\TraversalRules}

Example Implementation

To be done.

Notes

The :test-not parameter is deprecated.

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