NAME
    isprime - whether a small integer is prime

SYNOPSIS
    isprime(x [,err])

TYPES
    x		int
    err		int

    return	int

DESCRIPTION
    Determine if x is is a small prime.	 This function will return
    1 if x is a small prime.  If x is even, this function will
    return 0.  If x is negative or a small composite (non-prime),
    0 will be returned.

    If x is a large positive odd value and the err argument is
    given, this function return err.  If x is a large positive odd
    value and the err argument is not given, an error will be
    generated.

    Note that normally this function returns the integer 0 or 1.
    If err is given and x is a large positive odd value, then err
    will be returned.

EXAMPLE
    > print isprime(-3), isprime(1), isprime(2)
    0 0 1

    > print isprime(21701), isprime(1234577), isprime(1234579)
    1 1 0

    > print isprime(2^31-9), isprime(2^31-1), isprime(2^31+11)
    0 1 1

    > print isprime(2^32+1, -1), isprime(3^99, 2), isprime(4^99, 2)
    -1 2 0

LIMITS
    err not given  and	(y is even  or	y < 2^32)

LINK LIBRARY
    FLAG zisprime(ZVALUE x)	(return 1 if prime, 0 not prime, -1 if >= 2^32)

SEE ALSO
    factor, lfactor, nextprime, prevprime, pfact, pix,
    isassoc, isatty, isblk, isconfig, isdefined, iserror, iseven, isfile,
    ishash, isident, isint, islist, ismat, ismult, isnull, isnum, isobj,
    isobjtype, isodd, isrand, israndom, isreal, isrel,
    issimple, issq, isstr, istype

## Copyright (C) 1999  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.2 $
## @(#) $Id: isprime,v 29.2 2000/06/07 14:02:33 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/isprime,v $
##
## Under source code control:	1994/10/21 02:21:29
## File existed as early as:	1994
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/