(not item)

Determine whether an item is nil.

This function determines whether item is nil. If it is nil, a T is returned. If it is not nil, nil is returned.

Examples

Code	Returns
(not "Yes!")	nil
(not (> 5 6))	T

NOTE The not and the null functions are very similar. The difference is that null checks whether the item is bound to nil. Null is meant for testing for empty lists.

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(numberp item)

(type item)

LISP Compatibility

Programming Overview of LISP (LISt Processing) Language