Re: [FWP] 4 Consecutive Letters

[Ronald J Kimball <rjk@linguist.dartmouth.edu>]

On Mon, Aug 14, 2000 at 11:29:04AM -0500, Tim Ayers wrote:
> >>>>> "R" == Ronald J Kimball <rjk@linguist.dartmouth.edu> writes:
> R> Here's my first solution:
> R>   perl -ne'@a=a..z;for$i(0..22){print,last if/@{[$a[$i]..$a[$i+3]]}/x}'
> 
> R> And a slightly shorter one:
> R>   perl -ne'for$i(97..119){print,last if/@{[map chr,$i..$i+3]}/x}'
> 
> Ronald's first solution seems to be able to be modified to be shorter:
> 
>      perl -ne'@a=a..z;for$i(0..22){print,last if/@a[$i..$i+3]/x}'

I can't believe I didn't see that.


> At least this appears to work for me in 5.005_03 and 5.6.0.
> 
> Ronald, would you explain what the /x modifier is doing here?  It
> doesn't work without it, but I thought /x was just to allow
> expressive/expanded regexes. I have a hypothesis, but I personally
> couldn't find anything in L<perlre> or Camel v3. Thank you.

/@a[$i..$i+3]/ interpolates @a[$i..$i+3] as join($", @a[$i..$i+3]),
resulting in a regex like /a b c d/.  But we need a regex like /abcd/.
One solution would be to set $" to '', but a shorter solution is to use
/x, which tells Perl to ignore the whitespace in the regex.


Ronald

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