count quotes in a string that do not have a backslash before them.

Question

Hey I'm trying to use a regex to count the number of quotes in a string that are not preceded by a backslash.. for example the following string:

• "\"Some text
• "\"Some \"text

The code I have was previously using String#count('"') obviously this is not good enough

When I count the quotes on both these examples I need the result only to be 1

I have been searching here for similar questions and ive tried using lookbehinds but cannot get them to work in ruby.

I have tried the following regexs on Rubular from this previous question

• /[^\\]"/
• ^"((?<!\\)[^"]+)"
• ^"([^"]|(?<!\)\\")"

None of them give me the results im after

Maybe a regex is not the way to do that. Maybe a programatic approach is the solution

Thanks --Rob

Answer 1

How about string.count('"') - string.count("\\"")?

Answer 2

result = subject.scan(
    /(?:        # match either
     ^         # start-of-string\/line
    |          # or
     \G        # the position where the previous match ended
    |          # or
     [^\\]     # one non-backslash character
    )          # then
    (\\\\)*    # match an even number of backslashes (0 is even, too)
    "          # match a quote/x)

gives you an array of all quote characters (possibly with a preceding non-quote character) except unescaped ones.

The \G anchor is needed to match successive quotes, and the (\\\\)* makes sure that backslashes are only counted as escaping characters if they occur in odd numbers before the quote (to take Amarghosh's correct caveat into account).