From f45ab30c0b627099fedf57946a469f8d29a32915 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 27 Apr 2022 12:07:20 +0200 Subject: [PATCH] factor: --exponents: new option for printing in p^e format When factoring numbers that have a large 2^n factor, it can be hard to eyeball just how many 2's there are. Add an option to print each prime power factor in the p^e format (omitting the exponent when it is 1). * src/factor.c: Add -h, --exponents option for printing in p^e format. * doc/coreutils.texi (factor invocation): Document the new option. * tests/misc/factor.pl: Add test case. * THANKS.in: Add previous suggester (https://lists.gnu.org/r/coreutils/2017-11/msg00015.html). Suggested-by: Emanuel Landeholm Signed-off-by: Rasmus Villemoes --- NEWS | 5 +++++ THANKS.in | 1 + doc/coreutils.texi | 24 ++++++++++++++---------- src/factor.c | 29 +++++++++++++++++++++++++---- tests/misc/factor.pl | 5 ++++- 5 files changed, 49 insertions(+), 15 deletions(-) diff --git a/NEWS b/NEWS index 3a9148637..16984003c 100644 --- a/NEWS +++ b/NEWS @@ -13,6 +13,11 @@ GNU coreutils NEWS -*- outline -*- long been documented to be platform-dependent. [bug introduced 1999-05-02 and only partly fixed in coreutils-8.14] +** New Features + + factor now accepts the --exponents (-h) option to print factors + in the form p^e, rather than repeating the prime p, e times. + * Noteworthy changes in release 9.1 (2022-04-15) [stable] diff --git a/THANKS.in b/THANKS.in index 311196a04..c67a64b88 100644 --- a/THANKS.in +++ b/THANKS.in @@ -188,6 +188,7 @@ Eivind eivindt@multinet.no Elbert Pol elbert.pol@gmail.com Eldon Stegall eldon@eldondev.com Eli Zaretskii eliz@is.elta.co.il +Emanuel Landeholm emanuel.landeholm@gmail.com Emile LeBlanc leblanc@math.toronto.edu Emmanuel Lacour elacour@home-dn.net Eric Backus ericb@lsid.hp.com diff --git a/doc/coreutils.texi b/doc/coreutils.texi index b1ec7c61c..7bca37b71 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -18619,26 +18619,30 @@ These programs do numerically-related operations. @pindex factor @cindex prime factors -@command{factor} prints prime factors. Synopses: +@command{factor} prints prime factors. Synopsis: @example -factor [@var{number}]@dots{} -factor @var{option} +factor [@var{option}]@dots{} [@var{number}]@dots{} @end example If no @var{number} is specified on the command line, @command{factor} reads numbers from standard input, delimited by newlines, tabs, or spaces. -The @command{factor} command supports only a small number of options: +The program accepts the following options. Also see @ref{Common options}. @table @samp -@item --help -Print a short help on standard output, then exit without further -processing. +@item -h +@itemx --exponents +@opindex -h +@opindex --exponents +print factors in the form @math{p^e}, rather than repeating +the prime @samp{p}, @samp{e} times. If the exponent @samp{e} is 1, +then it is omitted. -@item --version -Print the program version on standard output, then exit without further -processing. +@example +$ factor --exponents 3000 +3000: 2^3 3 5^3 +@end example @end table If the number to be factored is small (less than @math{2^{127}} on diff --git a/src/factor.c b/src/factor.c index 66ce28b84..ca315c2b0 100644 --- a/src/factor.c +++ b/src/factor.c @@ -226,12 +226,16 @@ enum static struct option const long_options[] = { + {"exponents", no_argument, NULL, 'h'}, {"-debug", no_argument, NULL, DEV_DEBUG_OPTION}, {GETOPT_HELP_OPTION_DECL}, {GETOPT_VERSION_OPTION_DECL}, {NULL, 0, NULL, 0} }; +/* If true, use p^e output format. */ +static bool print_exponents; + struct factors { uintmax_t plarge[2]; /* Can have a single large factor */ @@ -2457,6 +2461,12 @@ print_factors_single (uintmax_t t1, uintmax_t t0) { lbuf_putc (' '); print_uintmaxes (0, factors.p[j]); + if (print_exponents && factors.e[j] > 1) + { + lbuf_putc ('^'); + lbuf_putint (factors.e[j], 0); + break; + } } if (factors.plarge[1]) @@ -2525,6 +2535,11 @@ print_factors (char const *input) { putchar (' '); mpz_out_str (stdout, 10, factors.p[j]); + if (print_exponents && factors.e[j] > 1) + { + printf ("^%lu", factors.e[j]); + break; + } } mp_factor_clear (&factors); @@ -2542,15 +2557,17 @@ usage (int status) else { printf (_("\ -Usage: %s [NUMBER]...\n\ - or: %s OPTION\n\ +Usage: %s [OPTION] [NUMBER]...\n\ "), - program_name, program_name); + program_name); fputs (_("\ Print the prime factors of each specified integer NUMBER. If none\n\ are specified on the command line, read them from standard input.\n\ \n\ "), stdout); + fputs ("\ + -h, --exponents print repeated factors in form p^e unless e is 1\n\ +", stdout); fputs (HELP_OPTION_DESCRIPTION, stdout); fputs (VERSION_OPTION_DESCRIPTION, stdout); emit_ancillary_info (PROGRAM_NAME); @@ -2593,10 +2610,14 @@ main (int argc, char **argv) atexit (lbuf_flush); int c; - while ((c = getopt_long (argc, argv, "", long_options, NULL)) != -1) + while ((c = getopt_long (argc, argv, "h", long_options, NULL)) != -1) { switch (c) { + case 'h': /* NetBSD used -h for this functionality first. */ + print_exponents = true; + break; + case DEV_DEBUG_OPTION: dev_debug = true; break; diff --git a/tests/misc/factor.pl b/tests/misc/factor.pl index a12768bf3..f399656c7 100755 --- a/tests/misc/factor.pl +++ b/tests/misc/factor.pl @@ -89,6 +89,8 @@ my @Tests = ['bug-gmp-plus_2_sup_128_plus_1', '+170141183460469231731687303715884105729', {OUT => '3 56713727820156410577229101238628035243'}], + ['h-1', '-h 3000', {OUT => '2^3 3 5^3'}], + ['h-2', '3000 --exponents', {OUT => '2^3 3 5^3'}], ); @@ -99,7 +101,8 @@ my $t; Test: foreach $t (@Tests) { - (my $arg1 = $t->[1]) =~ s| *\+?||; + (my $arg1 = $t->[1]) =~ s| *\+?||; # strip '+' + (my $arg1 = $arg1) =~ s| *-[^ ]+ *||; # strip option # Don't fiddle with expected OUT string if there's a nonzero exit status. foreach my $e (@$t) -- 2.26.2