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)

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