Hello everybody
Incrementing and decrementing strings are quiet puzzling to me. I don't seem
to figure out the rationale behind the use of the increment (++) and decrement
(--) operators when it comes to strings. Let me illustrate:
$str = 'hello';
$str++;
print "$str\n"; # here we get "hellp". Basically perl adds one to the letter
'o' making it 'p'
$str--;
print "$str\n"; # here we get -1
# since the value of $str was 'hellp'
# which is evaluated to 0, decremented to -1
$str = 'az';
$str++;
print "$str\n"; # what do we get? 'ba' because 'z' is the last
# letter of the alphabet, so, z+1 = a and one at hand,
# adding it to 'a' to get 'ba'. hmmm
$str = '1b';
$str++;
print "$str\n"; # we get 2 here, since '1b' =~ 1 when evaluated at a numeric
context
$str = 'b1';
$str++;
print "$str\n"; # what do we get here? 'b2'
$str = 'ab1';
$str++;
print "$str\n"; # can you take a guess? Answer: 'ac0'
$str = 'ab1a';
$str++;
print "$str\n"; # 'ab1a' evaluates to 0, so incrementing it gets us to 1
Maybe you can make out a rule for what happens in every case (just like the
nested if-statements in the code Perl_sv_inc at sv.c lines 4605-4725 of the
stable perl-5.6.1 distribution).
So, is there a rational reason why the increment operator should behave this
way and why the decrement operator behaves differently?
(maybe this was not a beginners question, but it may help eleminate some
possible future frustration).
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