Re^2: .. operator and not including the condition of right operand

In the "perverse" category:

use strict;
use warnings;
my @aap = qw( 0aap 0noot 1mies 2mies 0aap 0noot 1mies 6mies );
for (@aap) {
  print "$_\n" if - reverse '0' . (/^1(.*)/ .. /^0(.*)/);
}
__END__
1mies
2mies
1mies
6mies
[download]

I wonder what's more common, the situation described by the OP or the need to know the sequence number of the match? If the former is more common, then I think one could make the case for having the match of the right operand return a string of the form '0En' instead of the current 'nE0'. Then, all that would be required to satisfy the OP's request would be to prepend 0+, or better yet, a minus sign, in front of the .. expression:

if ( -(/^1(.*)/../^0(.*)/) )
[download]

whereas if one wanted to keep the line matching the right operand one would omit the 0+ or minus sign:

if ( (/^1(.*)/../^0(.*)/) )
[download]

Those who actually wanted the match number, would have to scrape it off the return value:

if ( ( /^1(.*)/../^0(.*)/ ) =~ /(\d+)$/ ) {
  # $1 contains the sequence number of match
[download]

I've tested this scheme a bit, and it seems to work; please let me know if I missed some corner (or not-so-corner) cases.

the lowliest monk

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Re^3: .. operator and not including the condition of right operand by bart (Canon) on Apr 28, 2005 at 06:23 UTC
The reason for appending "E0" is that the value in numerical context is unchanged: "3E0" as an integer is 3 (just like "3E1" is 30; not because numification ignores everything from the "E" till the end). Your value would means zero. And I don't think `0+$count` is easier than `$count =~ /E/`. Nor faster, or much faster at least. Your `/(\d+)$/` definitely isn't easy, nor likely very fast. As you can guess from the generally unknown behaviour of what `..` actually returns, neither requirements are very common. That's why I'm most happy with the status, like it is.	[reply] [d/l] [select]
Re^4: .. operator and not including the condition of right operand by tlm (Prior) on Apr 28, 2005 at 12:18 UTC
I realize that `0E3` means 0 in numeric context; that's precisely the point. In fact it is "a true zero", because in string context it evaluates to true. The nice thing about this is that simply by prepending a minus sign (or 0+, or 0!=) to the expression one selectively alters the truth value only of the value returned by `..` when its right operand is matched; the truth of all the other values returned by this operator remains unchanged. Therefore, with a tiny change one can choose between keeping or discarding the line corresponding to a right-operand match. BTW, to use `/E/` for the original problem, you'd need two tests and an assignment: `if ( my $count = /^1(.)/../^0(.)/ and $count !~ /E/ )` [download] which is significantly longer and more involved than `if ( -( /^1(.)/../^0(.)/ ) )` [download] To use a regex to solve this problem one would need `/^\d+$/`: `if ( ( /^1(.)/../^0(.)/ ) =~ /^\d+$/ )` [download] (This is basically one of the solutions that Roy Johnson proposed.) the lowliest monk	[reply] [d/l] [select]