## LIBRARY

```(import (rnrs))                     ;R6RS
(import (rnrs base))                ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS
(import (rnrs arithmetic flonums))  ;R6RS
(import (rnrs arithmetic fixnums))  ;R6RS
```

## SYNOPSIS

```(negative? x)
(positive? x)
(odd? n)
(even? n)

;; R6RS
(flnegative? fl)
(flpositive? fl)
(flodd? fl)
(fleven? fl)
(fxnegative? fx)
(fxpositive? fx)
(fxodd? fx)
(fxeven? fx)
```

## DESCRIPTION

These numerical predicates test a number object for a particular property, returning #t or #f.
Properties tested
The predicates tests the following properties.
```  [1mzero?     [22mtests if the number is = to zero
[1mpositive?   [22mtests if the number is greater than zero
[1mnegative?   [22mtests if the number is less than zero
[1modd?      [22mtests if the number is odd
[1meven?     [22mtests if the number is even
```
Flonum variants
These variants restrict their arguments to flonums.
Fixnum variants
These variants restrict their arguments to fixnums.

Unless the number is exact, the results may be unreliable because a small inaccuracy may affect the result.

## RETURN VALUES

Returns a single value; a boolean.

## EXAMPLES

```(zero? +0.0)        =>  #t
(zero? -0.0)        =>  #t
(zero? +nan.0)      =>  #f
(positive? +inf.0)  =>  #t
(negative? -inf.0)  =>  #t
(positive? +nan.0)  =>  #f
(negative? +nan.0)  =>  #f
```

## COMPATIBILITY

These procedures work the same in all Scheme revisions since R2RS.

## ERRORS

This procedure can raise exceptions with the following condition types:
&assertion (R6RS)
The wrong number of arguments was passed or an argument was outside its domain.
R7RS
The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically.

>(3scm), finite?(3scm)

## STANDARDS

R4RS, IEEE Scheme, R5RS, R6RS, R7RS

## HISTORY

These procedures were first introduced in R2RS. Scheme before then, running on MacLisp, had access to similar predicates: zerop, plusp, minusp, and oddp. LISP 1.5 had a minusp predicate that returned true for negative numbers, including -0. It also had zerop and onep predicates. These were specified to true when the absolute difference between the argument and zero or one, respectively, is less than 3e-6.

## AUTHORS

This page is part of the scheme-manpages project. It includes materials from the RnRS documents. More information can be found at `https://github.com/schemedoc/manpages/`.

Markup created by unroff 1.0sc,    March 04, 2023.