I've spent some time, but still have to solution. I need regular expression that is able to match a words with signs in it (like c++) in string.
I've used /\bword\b/, for "usual" words, it works OK. But as soon as I try /\bC\+\+\b/ it just does not work. It some how works wrong with a plus signs in it.
I need a regex to detect if input string contains c++ word in it. Input like,
"c++ developer"
"using c++ language"
etc.
ps. Using C#, .Net Regex.Match function.
Thanks for help!
+ is a special character so you need to escape it
\bC\+\+(?!\w)
Note that we can't use \b because + is not a word-character.
The problem isn't with the plus character, that you've escaped correctly, but the \b sequence. It indicates a word boundary, which is a point between a word character (alphanumeric) and something else. Plus isn't a word character, so for \b to match, there would need to be a word character directly after the last plus sign.
\bC\+\+\b matches "Test C++Test" but not "Test C++ Test" for example. Try something like \bC\+\+\s if you expect there to be a whitespace after the last plus sign.
Plus sign have special meaning so you will have to escape it with \. The same rule applies to these characters: \, *, +, ?, |, {, [, (,), ^, $,., #, and white space
UPDATE: the problem was with \b sequence
If you want to match a c++ between non-word chars (chars other than letters, digits and underscores) you may use
\bc\+\+\B
See the regex demo where \b is a word boundary and \B matches all positions that are not word boundary positions.
C# syntax:
var pattern = @"\bc\+\+\B";
You must remember that \b / \B are context dependent: \b matches between the start/end of string and the adjoining word char or between a word and a non-word chars, while \B matches between the start/end of string and the adjoining non-word char or between two word or two non-word chars.
If you build the pattern dynamically, it is hard to rely on word boundary \b pattern.
Use adaptive dynamic wod boundaries, (?!\B\w) and (?<!\w\B) lookarounds instead, they will always match a word not immediately preceded/followed with a word char if the word starts/ends with a word char:
var pattern = $@"(?!\B\w){Regex.Escape(word)}(?<!\w\B)";
If the word boundaries you want to match are whitespace boundaries (i.e. the match is expected only between whitespaces), use
var pattern = $@"(?<!\S){Regex.Escape(word)}(?!\S)";
As the others said, your problem isn't the + sign you've escaped correctly but the \b that is a zero-lenght char that match word boundary that takes place between word \w and non-word \W char.
There is also another mistake in your regex, you want to match char C (uppercase) with c++ (lowercase).To do so you have to change your regex to /\bc\+\+/ or use the i modifier to match case insensitive : /\bc\+\+/i
