Question

I’m trying to wrap parentheses around string in ruby, only if it isn’t wrapped yet:

"my string (to_wrap)" => "my string (to_wrap)"
"my string to_wrap" => "my string (to_wrap)"

I’ve tried something like:

to_wrap = 'to_wrap'
regexp = Regexp.new "(?!\()#{to_wrap}(?!\))"
string.sub(regexp, "(#{to_wrap})")

but it does not work.

Thanks in advance!

Answer 1

You are very close. Your first negative lookaround is a lookahead, though. So it looks at the first character of to_wrap. Just make that a lookbehind:

"(?<!\()#{to_wrap}(?!\))"

And just to present you with an alternative option to escape parentheses (it’s really a matter of taste which on to use, but I find it more easily readable):

"(?<![(])#{to_wrap}(?![)])"