in reply to Regex Question

This should work:

    $field =~ s/
                (?<!C)      # not preceeded by "C"
                (?:\\|\/)   # back or forward slash
                (?!O)       # not succeeded by "O"
                |
                (?<!\d)     # not preceeded by digits
                (?:\\|\/)   # back or forward slash
                (?!\d)      # not succeeded by digits
            / & /xg;        # replace with '&' (globally)

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Nope; wrong. I realised my blunder right after posting.

Makeshifts last the longest.

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Re^2: Regex Question
by Roy Johnson (Monsignor) on Nov 15, 2005 at 19:47 UTC
    You were bitten by negative-over-or-logic. The left side of the | will match what the right side is intended to skip. It has to be something like 
    $field =~ s/
  (?<!C(?=.O))   # Look back a character and make sure it's not C-some
+thing-O from there
  (?<!\d(?=.\d)) # Make sure it's also not a digit-something-digit
  (?:\\|\/)      # The something is a slash or backslash
/ & /xgi;

    [download]
    Caution: Contents may have been coded under pressure.
[reply]
[d/l]

      That won’t match the exact same things. The OP’s regex will replace the slash in "/2" or in "1/", yours won’t. Not sure if this is part of the spec, but it’s something to be aware of.

      Meh. That’s it, I’m going back to bed.

      Makeshifts last the longest.

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[d/l]
[select]
        Mine does replace the slash when it has a digit on only one side. The logic is that the slash is replaced unless there is a digit on both sides. It is the OP's logic that will not replace a slash with a digit on either side. 
        for my $field ( map $_, 'C/O', '2/4', 'C/2', 'd/l', '2/', '/2') {
  print "$field...";
  $field =~ s/
    (?<!C(?=.O))   # Look back a character and make sure it's not C-so
+mething-O from there
    (?<!\d(?=.\d)) # Make sure it's also not a digit-something-digit
    (?:\\|\/)      # The something is a slash or backslash
  / & /xgi;   
  print "$field\n";
}

        [download]
        Caution: Contents may have been coded under pressure.
[reply]
[d/l]
        Yes, that would comply with my specification of the problem. If there is only a digit on one side, replace the slash with an ampersand.
        I use the most powerful debugger available: print!
[reply]
Re^2: Regex Question
by ikegami (Patriarch) on Nov 15, 2005 at 19:43 UTC

    Nope. It replaces the slash in "9\\9" even though it shouldn't.

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[reply]
[d/l]

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