Whats with the autoincrementation of a string

bingalee has asked for the wisdom of the Perl Monks concerning the following question:

Im trying to figure this out but I dont get it. Here's the code

#!/usr/bin/perl
use warnings;
$a = "A9"; print ++$a, "\n";
$a = "bz"; print ++$a, "\n";
$a = "Zz"; print ++$a, "\n";
$a = "z9"; print ++$a, "\n";
$a = "9z"; print ++$a, "\n";
[download]

OUTPUT

>perl auto2.plx
B0
ca
AAa
aa0
10
>
[download]

I get the first two outputs, A turns to B and 9 to 0.

But how does "Zz" become "AAa", "z9" become "aa0" and so on.. *confused*

Comment on Whats with the autoincrementation of a string Select or Download Code

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Re: Whats with the autoincrementation of a string by space_monk (Chaplain) on Jun 14, 2013 at 18:54 UTC
Note that the incrementation sequences are `0..9 => 0 + carry\|1 i.e 10 A..Z => A + carry\|A i.e. AA a..z => a + carry\|a i.e aa` [download] bz => ca wrapping the z->a gives a carry to the b next in Lower a..z is c. Zz => AAa wrapping the z->a gives a carry to the Z next in Upper case A..Z is AA. z9 => aa0 incrementing 9 wraps round to zero, passing a carry up to the z. Next up from z is aa 9z => 10 tricked you!! - string autoincrement only works on patterns matching regex `/^[a-zA-Z][0-9]\z/`, this doesn't match that pattern, so treats leading number(s) as the (numeric?) value and increments that. 9 goes to 10 :-) Read more... (32 Bytes) If you spot any bugs in my solutions, it's because I've deliberately left them in as an exercise for the reader! :-)	[reply] [d/l] [select]
Re^2: Whats with the autoincrementation of a string by bingalee (Acolyte) on Jun 18, 2013 at 20:03 UTC
ok, so what about something that doest end with a "z" or a "9". Like will "zc" become "aad?"	[reply]
Re^3: Whats with the autoincrementation of a string by choroba (Cardinal) on Jun 18, 2013 at 20:06 UTC
No, "zc" will become "zd". Similarly, 93 + 1 = 94, not 104. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply]
Re^4: Whats with the autoincrementation of a string by bingalee (Acolyte) on Jun 18, 2013 at 21:19 UTC
Re^5: Whats with the autoincrementation of a string by space_monk (Chaplain) on Jun 19, 2013 at 05:52 UTC
Some notes below your chosen depth have not been shown here
Re: Whats with the autoincrementation of a string by LanX (Saint) on Jun 14, 2013 at 18:56 UTC
Think of every position as a wheel in a mechanical counter. There are three kinds of wheels 0-9, a-z and A-Z which can be independently be chosen for each position. Clearer now? =) edit perlop `the increment is done as a string, preserving each character within its range, with carry: print ++($foo = '99'); # prints '100' print ++($foo = 'a0'); # prints 'a1' print ++($foo = 'Az'); # prints 'Ba' print ++($foo = 'zz'); # prints 'aaa'` [download] Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l]
Re^2: Whats with the autoincrementation of a string by space_monk (Chaplain) on Jun 14, 2013 at 20:09 UTC
Not quite independently. Any numeric wheels must be at the back. e.g. 'Aa00' will work, '00Aa' won't. If you spot any bugs in my solutions, it's because I've deliberately left them in as an exercise for the reader! :-)	[reply]
Re^3: Whats with the autoincrementation of a string by LanX (Saint) on Jun 14, 2013 at 21:36 UTC
Sure, anything with leading digits which isn't a proper number is dealt by atoi in numeric context, IIRC that's due to some C legacy. `DB<109> @a=a..c => ("a", "b", "c") DB<110> $a[" 1x"] => "b"` [download] plz note: only with `no warnings`! Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l] [select]

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