negative?, positive?, odd?, even?, flnegative?, flpositive?, flodd?, fleven?, fxnegative?, fxpositive?, fxodd?, fxeven?- numerical predicates

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. 
  zero?     tests if the number is = to zero
positive?   tests if the number is greater than zero
negative?   tests if the number is less than zero
  odd?      tests if the number is odd
  even?     tests 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.

SEE ALSO

>(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.