Consecutive Numbers

[Ilya Zakharevich]

[A complimentary Cc of this posting was NOT [per weedlist] sent to
Ilya Zakharevich

[A complimentary Cc of this posting was NOT [per weedlist] sent to
Graham Drabble

I have a file that contains a list of numbers. I'm trying to process
the file to find out how many rows start with 4 consecutive digits
(either ascending or decending). Currently I've got

I'm puzzled at all complications: what is wrong with using something like

my $four = substr $in, 0, 4;
print 'OK' if length $four == 4 and
(0 <= index '0123456789', $four or 0 <= index '9876543210', $four);

Or one can try something like

my $four = substr $in, 0, 4;
print 'OK' if length $four == 4 and
0 <= index "0123456789\x{FFFFFFFF}9876543210", $four;

for its speed. However, the Unicode overhead can eat the advantages
of fewer opcodes to dispatch...

Yours,
Ilya

P.S. Here I use the fact that utf8 character repertuar is larger than
UTF-8 one.