in reply to Magical Auto-Decrement

Nice try, but of course, the issue re. the boundary cases still holds, so the following 
--"a" gives "z"
--"a00" gives "z99"
--"0" gives "9"
--"aa00" gives "zz99"

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give results which aren't reversible. Update: (following comment below)

Yes, you should eat the left-char on underflow, and --"a" => undef and --0 => undef.

I was going to make a point about keeping items in the right order for a sort, but of course zz++ == aaa which screws up that point. Hmmm...
--
Brovnik

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Re: Re: Magical Auto-Decrement
by John M. Dlugosz (Monsignor) on Jul 04, 2001 at 21:40 UTC
    Looks like increment will add another character upon overflow, presumably duplicating the kind of the previous leftmost. To undo ++, the -- could eat the leftmost upon underflow. But ++ can't always be the exact opposite since it doesn't know which kind of character to add.

    I'm aware that I'm clamping on underflow. It's a snippet, not a polished module! It was done more for the challange, but if I really needed this (like the poster that inspired it), I'd have the function croak or something, if this was significant to the program.

    —John

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