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(elisp)Predicates on Numbers

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Type Predicates for Numbers
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   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 Note: 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)'.