in reply to flip-flop interpolation

Range Operators says:
If either operand of scalar .. is a constant expression, that operand is considered true if it is equal (==) to the current input line number (the $. variable).
So, if you're not using constants, you have to do the comparison yourself: 
print if ($. == $i) .. ($. == $j); # The parentheses are optional.

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Re^2: flip-flop interpolation
by Anonymous Monk on May 13, 2015 at 10:31 UTC
    Thank you.
    And can't I say to Perl to use my $i and $j as constants?
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      That is like asking to draw a red line using green ink :)

      The way to do it is to use the green ink to define a universe containing hardcoded red lines:

      #untested, and quite silly
eval "print $_ if $i .. $j;";

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[d/l]

      You could use the constant pragma but it is not really saving you anything.

      $ seq 1 6 > lines
$ cat lines
1
2
3
4
5
6
$ perl -ne '
> use constant { I => 3, J => 5 };
> print if I .. J;' lines
3
4
5
$

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      I hope this is of interest.

      Cheers,

      JohnGG

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[d/l]
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