null

Type:	-	predicate function (subr)
Source:	-	xlbfun.c

Syntax

(null expr)

expr - the expression to check
returns -  T  if the list is empty, NIL otherwise

Description

The 'null' predicate function checks 'expr' for an empty list.  T  is returned if the list is empty, NIL is returned otherwise. The 'expr' does not have to be a valid list, but if it is not a list then NIL is returned as the result.

Examples

(null '())     ; returns T - empty list
(null ())      ; returns T - still empty
(setq a NIL)   ; set up a variable
(null a)       ; returns T - value = empty list

(null "a")     ; returns NIL - not a list
(null 'a)      ; returns NIL - not a list

Note: The 'null' predicate function is the same function as the not predicate function.

See the null predicate function in the XLISP 2.0 manual.

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