Re: Multiple Conditional Statements

[BillKSmith]

If you like a more direct approach,

use strict;
use warnings;
use List::MoreUtils qw(any);
my ($RB1, $RB2) = (1,2);
my ($WR1, $WR2) = (3,4);
my  $TE1         = 1;

my $match;
my @a = \($RB1, $RB2, $WR1, $WR2, $TE1);
for my $i (0..3){
    $match |= any {${$a[$i]} == $$_} @a[$i+1 .. 4];
}
print "No " if !$match;
print "match\n";

You could use grep in place of any (List::MoreUtils), but the name 'any' seems to convey the intent better.

[BrowserUk]

If you like a more direct approach,

That's a perfectly valid approach, but how is it "more direct"? (And "more direct" that what for that matter?)

You have:

1. An auxiliary boolean variable;
2. An auxiliary array (... of references which have to be taken);
3. Two nested loops;
4. A callback function (from a module);
5. An array slice;
6. n(n+1) dereferences;
7. n(n+1)/2 comparisons;
8. And it doesn't even short-circuit if the first two variables compared are the same.

That's the strangest definition of "more direct" I can think of :)

[BillKSmith]

Of course I agree with all your arguments. All I meant to imply was that it directly compares the variables in question (not copies) and with very little source code. I find it very easy to understand. In general, that should trump issues of speed, memory, or namespace.

[BrowserUk]

I find it very easy to understand. In general, that should trump issues of speed, memory, or namespace.

Interesting justifiction. Personally, I prefer solutions that are:

1. Clean.

   Don't create persistent, named temporaries to clutter, conflict and confuse the purpose of the code.

2. Clear.

   Don't introduce unnecessary (and counterproductive) levels of indirection in the name of premature optimisation (avoiding copies).

   It is more expensive to takes references then dereference those references; than to make copies of simple, small scalar values:

   ($a,$b,$c,$d,$e) = 1 .. 5; 
   cmpthese -1,{
       a=>q[ my @a = ($a,$b,$c,$d,$e); ++$_ for @a;],
       b=>q[my @a = \($a,$b,$c,$d,$e); ++$$_ for @a; ] 
   };;
         Rate    b    a
   b 525790/s   -- -23%
   a 685872/s  30%   --
   

3. Concise.

   The goal of this snippet if to cross-compare a few variables with the only interest being a single boolean truth.

   Spreading that across half a dozen lines, adding named temporaries to the mix; adding a module, a callback and nested loops; and obscure indirections to derive a simple boolean does the very opposite of making things easy to understand.

4. Simple.

   Simple means when the algorithm calls for:

   if( <some condition> ) {
      ## do somthing
   }
   

   the implementation (code) should reflect that. Not detract from the algorithm by introducing unneeded complexity.

5. Efficient.

   looping to perform all 15 comparisons when the first or the second can resolve the boolean condition is just flagrant waste.