NAME
    prevprime - nearest prime less than specified number

SYNOPSIS
    prevprime(n [,err])

TYPES
    n		real
    err		integer

    return	positive integer or err

DESCRIPTION
    If n is an integer and 2 < n < 2^32, prevprime(n) returns the
    nearest prime less than n.

    If n <= 2 or >= 2^32 or n is fractional, prevprime(n, err)
    returns the value of err.

    Other cases cause a runtime error.

EXAMPLE
    ; print prevprime(10), prevprime(100), prevprime(1e6)
    7 97 999983

    ; print prevprime(2,-99), prevprime(2^32,-99)
    -99 -99

    ; print prevprime(2)
    pprime arg 1 is <= 2

LIMITS
    2 < n < 2^32

LINK LIBRARY
    FULL zpprime(ZVALUE z)

SEE ALSO
    factor, isprime, lfactor, nextcand, nextprime, prevcand,
    pfact, pix, ptest

## Copyright (C) 1999-2006  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.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## @(#) $Revision: 30.1 $
## @(#) $Id: prevprime,v 30.1 2007/03/16 11:10:42 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/prevprime,v $
##
## Under source code control:	1995/12/18 12:34:58
## File existed as early as:	1995
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/