freebsd-skq/games/factor/factor.6
cperciva a742fc39b4 Switch primes(6) from using unsigned long to using uint64_t. This fixes
'limited range of type' warnings about comparisons on 32-bit systems, and
allows 32-bit systems to compute the full range of primes.
2014-09-27 09:00:38 +00:00

128 lines
3.9 KiB
Groff

.\" Copyright (c) 1989, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Landon Curt Noll.
.\"
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.\" @(#)factor.6 8.1 (Berkeley) 5/31/93
.\"
.\" $FreeBSD$
.\"
.\" By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
.\"
.\" chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
.\"
.Dd October 10, 2002
.Dt FACTOR 6
.Os
.Sh NAME
.Nm factor , primes
.Nd factor a number, generate primes
.Sh SYNOPSIS
.Nm
.Op Fl h
.Op Ar number ...
.Nm primes
.Op Fl h
.Op Ar start Op Ar stop
.Sh DESCRIPTION
The
.Nm
utility will factor positive integers.
When a number is factored, it is printed, followed by a
.Ql \&: ,
and the list of factors on a single line.
Factors are listed in ascending order, and are preceded by a space.
If a factor divides a value more than once, it will be printed more than once.
.Pp
When
.Nm
is invoked with one or more arguments, each argument will be factored.
.Pp
When
.Nm
is invoked with no arguments,
.Nm
reads numbers, one per line, from standard input, until end of file or error.
Leading white-space and empty lines are ignored.
Numbers may be preceded by a single
.Ql + .
Numbers are terminated by a non-digit character (such as a newline).
After a number is read, it is factored.
.Pp
The
.Nm primes
utility prints primes in ascending order, one per line, starting at or above
.Ar start
and continuing until, but not including
.Ar stop .
The
.Ar start
value must be at least 0 and not greater than
.Ar stop .
The
.Ar stop
value must not be greater than the maximum.
The default and maximum value of
.Ar stop
is 3825123056546413050.
.Pp
When the
.Nm primes
utility is invoked with no arguments,
.Ar start
is read from standard input and
.Ar stop
is taken to be the maximum.
The
.Ar start
value may be preceded by a single
.Ql + .
The
.Ar start
value is terminated by a non-digit character (such as a newline).
.Sh DIAGNOSTICS
.Bl -diag
.It "negative numbers aren't permitted"
.It "illegal numeric format"
.It "start value must be less than stop value"
.It "Result too large"
.El
.Sh BUGS
.Nm
cannot handle the
.Dq "10 most wanted"
factor list,
.Nm primes
will not get you a world record.
.Pp
.Nm primes
is unable to list primes between 3825123056546413050 and 18446744073709551615
since it relies on strong pseudoprime tests after sieving, and nobody has
proven how many strong pseudoprime tests are required to prove primality for
integers larger than 3825123056546413050.