Denis, you have not told us whether your flags are mutually exclusive ($a can contain ABA - only) or they can be turned on at the same time ($a can contain ABA and SCO).

In the olden days, in the caves, they used *flags*. Each flag was denoted by a digit in a binary word. The binary word making up the "options". Flags as binary words had the added benefit of having a bunch of them turned on at the same time. The negative side is that they are all binary/integers and made little sense to the user without consulting the manual - though most times they were internal and nobody cared about their values, e.g. C's open()'s O_CREAT and O_APPEND flags.

Here is a refresher (translated from C):

#!/usr/bin/env perl
use strict;
use warnings;

use Getopt::Long;
# our constants
use constant ABA => 0b00001; # 0b... for binary number
use constant SCO => 0b00010;
use constant ACC => 0b00100;

my $a = 0b0;

Getopt::Long::GetOptions(
  'ABA' => sub { $a |= ABA },
  'SCO' => sub { $a |= SCO },
  'ACC' => sub { $a |= ACC },
) or die "error command line";

if( $a & SCO ){ print "it has SCO!\n"; }
if( $a & ABA ){ print "it has ABA!\n"; }
if( $a & ACC ){ print "it has ACC!\n"; }

[download]

This is quite fast but I am sure there will be aesthetic objections including mine (which balances with my sentimental counter-objections).

In the Present, we do away with all these and instead use string constants and string comparisons which are more expensive.

I will not push any further the point of "cost" and "speed", but I will highlight the point of "multiple flags coexisting in a variable". Which is very useful as it reflects real-life situations. I am sure whizkids can make flags stored in strings turned on at the same time by devising a way to encode them in a string which can be robust yet ... quite unreadable, like the binary flags.

Against the binary flags is the MAXINT limitation which let's say is 2^64, it will limit the max number of flags to check on to 64 :(

PS. If this forum were another, I am sure someone would have suggested a class for handling this kind of situations.

PS2. Flags and Semaphores!

In reply to Re: Sparing multiple 'or's by bliako
in thread Sparing multiple 'or's by Denis

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