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| ANSI Common Lisp 14 Conses 14.2 Dictionary of Conses
14.2.48 subsetp | Function
  Syntax: subsetp list-1 list-2 `&key` key test test-not generalized-boolean Arguments and Values: 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. 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:
       (setq cosmos '(1 "a" (1 2)))  (1 "a" (1 2))
       (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
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: Section 3.6 Traversal Rules and Side Effects Notes: The `:test-not` parameter is deprecated. Allegro CL Implementation Details: None.

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