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   GNU Emacs Lisp Reference Manual
3.3: Type Predicates for Numbers
The functions in this section test whether the argument is a number or whether it is a certain sort of number. The functions integerp and floatp can take any type of Lisp object as argument (the predicates would not be of much use otherwise); but the zerop predicate requires a number as its argument. See also integer-or-marker-p and number-or-marker-p, in Predicates on Markers.
- Function: floatp object
- This predicate tests whether its argument is a floating point number and returns
t if so, nil otherwise. floatp does not exist in Emacs versions 18 and earlier.
- Function: integerp object
- This predicate tests whether its argument is an integer, and returns
t if so, nil otherwise.
- Function: numberp object
- This predicate tests whether its argument is a number (either integer or floating point), and returns
t if so, nil otherwise.
- Function: wholenump object
- The
wholenump predicate (whose name comes from the phrase ``whole-number-p'') tests to see whether its argument is a nonnegative integer, and returns t if so, nil otherwise. 0 is considered non-negative. natnump is an obsolete synonym for wholenump.
- Function: zerop number
- This predicate tests whether its argument is zero, and returns
t if so, nil otherwise. The argument must be a number. These two forms are equivalent: (zerop x) == (= x 0).
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