Follow the Fundamental Theory of Algebra. Disallow factorising of

numbers less than 2 as it is not
- naturally unique (negative numbers)
- finite (0)
- non-empty (1)

Discussed with the kristaps and wiz

diff --git a/factor/factor.6 b/factor/factor.6
index 69b1c535cda72dc9e839e543a08b4e6027e0fb6c..32029ecaa406cf3c3a4069c67778f911db753ef5 100644 (file)
--- a/factor/factor.6
+++ b/factor/factor.6
@@ -1,4 +1,4 @@
-.\"    $NetBSD: factor.6,v 1.11 2010/04/22 06:57:13 wiz Exp $
+.\"    $NetBSD: factor.6,v 1.12 2010/05/15 21:22:39 joerg Exp $
 .\"
 .\" Copyright (c) 1989, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -37,7 +37,7 @@
 .\"
 .\"   chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
 .\"
-.Dd April 22, 2010
+.Dd May 15, 2010
 .Dt FACTOR 6
 .Os
 .Sh NAME
@@ -49,7 +49,7 @@
 .Sh DESCRIPTION
 The
 .Nm
-utility factors positive integers.
+utility factors integers larger than 1.
 When a number is factored, it is printed, followed by a
 .Dq \&: ,
 and the list of
@@ -68,8 +68,8 @@ 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 \- or +, although negative numbers
-are rejected.
+Numbers may be preceded by a single +.
+Integer less than 2 are rejected.
 Numbers are terminated by a non-digit character (such as a newline).
 After a number is read, it is factored.
 Input lines must not be longer than

diff --git a/factor/factor.c b/factor/factor.c
index cc6c8b98ef0d81beef33f8c51e1fc3ae37f58f7d..10de005d0fa3efe21b46fc487578c3eb95613692 100644 (file)
--- a/factor/factor.c
+++ b/factor/factor.c
@@ -1,4 +1,4 @@
-/*     $NetBSD: factor.c,v 1.23 2010/05/13 17:52:11 tnozaki Exp $      */
+/*     $NetBSD: factor.c,v 1.24 2010/05/15 21:22:39 joerg Exp $        */
 
 /*
  * Copyright (c) 1989, 1993
@@ -42,7 +42,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993\
 #if 0
 static char sccsid[] = "@(#)factor.c   8.4 (Berkeley) 5/4/95";
 #else
-__RCSID("$NetBSD: factor.c,v 1.23 2010/05/13 17:52:11 tnozaki Exp $");
+__RCSID("$NetBSD: factor.c,v 1.24 2010/05/15 21:22:39 joerg Exp $");
 #endif
 #endif /* not lint */
 
@@ -177,7 +177,7 @@ main(int argc, char *argv[])
        else
                for (; *argv != NULL; ++argv) {
                        if (argv[0][0] == '-')
-                               errx(1, "negative numbers aren't permitted.");
+                               errx(1, "numbers <= 1 aren't permitted.");
                        if (BN_dec2bn(&val, argv[0]) == 0)
                                errx(1, "%s: illegal numeric format.", argv[0]);
                        pr_fact(val);
@@ -204,12 +204,8 @@ pr_fact(BIGNUM *val)
        const ubig *fact;               /* The factor found. */
 
        /* Firewall - catch 0 and 1. */
-       if (BN_is_zero(val))    /* Historical practice; 0 just exits. */
-               exit(0);
-       if (BN_is_one(val)) {
-               printf("1: 1\n");
-               return;
-       }
+       if (BN_is_zero(val) || BN_is_one(val))
+               errx(1, "numbers <= 1 aren't permitted.");
 
        /* Factor value. */