I was fiddling today with something that involved comparing strings and I thought that "Isn't a shame that the inequality operators don't return the point of divergance." I mean I think it would be nice to be able to say: 

if (my $pos=$str1 ne $str2) {
  print "A:$str1\nB:$str2\n";
  print "A and B are different at the $pos'th char (index ".($pos-1)."
+)\n";
}

[download]

Likewise for the other inequality operators.

Also castaway pointed out that if '0E0' is used to represent the divergance at index 0 then the overal return need not have the additional +1. OTOH it would mean the code would look like: 

if (my $pos=$str1 gt $str2) {
  $pos+=0;
  print "A:$str1\nB:$str2\n";
  print "The ".(1+$pos)."'th (index $pos) char in A is 'greater' than 
+that in B\n";
}

[download]

I'm not sure which exceptional behaviour I like more (adding one to the offset or using '0E0' as the return for index 0). But either way would more useful in many situations than the current True/False.

I wonder if this were to be added would it slow Perl down much? I would have thought that most of the extra stuff could be optimised away when the return won't be used... What do you think?

Minor Update: Presumably this behaviour could also extend to the numerical comparison operators by having it return the lower or greater value. So while != wouldn't be covered but the  > <  >= <= operators could return the relevent value so my $is_smaller=$x < 7; would set $is_smaller to $x (or 0E0 if it was 0) for all $x < 7; and it would set it to undef for all $x>=7. In which case obviously castaway's "0E0 for a 0" idea makes more sense than the offset+1, as it works in both the numerical inequality operators as well as the numerical. Although I have a feeling that something here would break perl as it currently works while I don't think thats true of the string comparisons.


---
demerphq

    First they ignore you, then they laugh at you, then they fight you, then you win.
    -- Gandhi

    Flux8


In reply to Should string inequality operators return the point the of divergance? by demerphq

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