I'm looking at writing a C++ syntax file, in which I hope to be able to highlight some blocks and constructs.

One thing I want to highlight is an if block. I've figured out how to highlight the whole block, by using a region with start and end markers. But now what I'd like to do is highlight parts of the block in different colours.

Specifically, I'd like to highlight the text within the parentheses, even if that text contains "()" itself.

For example, in the following block:

if (this is the() clause) {
    do something;
    do another thing;
}

I'd like to highlight the text "this is the() clause", but I cannot figure out the regex for this.

I have tried another region, which does capture some text within the parentheses:

:syntax region cppClause start=/\v\(/hs=e+1 end=/\v\)/he=s-1

But a) it stops the match if there is a ) character in the text, and b) I'm uncertain if I can nest this region, within the bigger if region which I have captured.

Is there a simpler way to do this?

I'm looking at writing a C++ syntax file, in which I hope to be able to highlight some blocks and constructs.

One thing I want to highlight is an if block. I've figured out how to highlight the whole block, by using a region with start and end markers. But now what I'd like to do is highlight parts of the block in different colours.

Specifically, I'd like to highlight the text within the parentheses, even if that text contains "()" itself.

For example, in the following block:

if (this is the() clause) {
    do something;
    do another thing;
}

I'd like to highlight the text "this is the() clause", but I cannot figure out the regex for this.

I have tried another region, which does capture some text within the parentheses:

:syntax region cppClause start=/\v\(/hs=e+1 end=/\v\)/he=s-1

But a) it stops the match if there is a ) character in the text, and b) I'm uncertain if I can nest this region, within the bigger if region which I have captured.

Is there a simpler way to do this?

• regex
• vim
• syntax

Share Improve this question Follow asked Feb 11 at 12:38 centauricentauri 7544 bronze badges 1

• You might be able to start from :help :syn-keepend which has an example like yours. You can define nested syntax groups so you'd have to define something that takes care of the inner parens. Getting it right can be tricky. – Friedrich Commented Feb 11 at 14:02

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2 Answers 2

Sorted by: Reset to default 2

For the regex patterns below I am using PRCE2 regex flavor, that should work with vim

If you want to capture the contents of the outer parenthesis on any one line, you can use this regex pattern (PRCE2 regex flavor):

 /\s\((.*)\)\s/g

Regex Demo: https://regex101/r/s7V8zk/9

NOTES:

• \s Start matching one whitespace before the first opening parenthesis.
• \( Match literal (, the first opening parenthesis.
• (.*) The capture group for the contents to be highlighted with different color. The dot (.) special character will match all characters except newline, including parenthesis. The dot followed by the star quantifier .* will match zero or more characters, and as many characters as possible to make a match, i.e. the * quantifier alone is greedy. The dot . matches all characters except newline character \n, so the .* will capture all characters until the very last ) before the end of line to make a match.
• \) Match literal ), the last closing parenthesis.
• \s Match one whitespace character.

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If you are only looking to match the contents of the outer parenthesis on an if-line, this regex pattern will do that job (PRCE2 regex flavor):

(?:^|\s)if\s(?:\w*\s)*\((.*)\).*\{

Regex Demo: https://regex101/r/K82Pml/6

NOTES:

• (?:...) Non-capturing group
• (?:^|\s) Match beginning of text ^ or | whitespace character \s, including newline
• if Matches a literal if
• \s Match one whitespace
• (?:\w*\s)* Match 0 or more * word characters \w (letters, numbers, underscore) followed by a whitespace character \s. Match this pattern 0 or more times (...)*.
• \( Match literal (, the first opening parenthesis.
• (.*) The capture group for the contents to be highlighted with different color. The dot (.) special character will match all characters except newline, including parenthesis. The dot followed by the star quantifier .* will match zero or more characters, and as many characters as possible to make a match, i.e. the * quantifier alone is greedy. The dot . matches all characters except newline character \n, so the .* will capture all characters until the very last ) before the end of line to make a match.
• \) Match literal ), the last closing parenthesis.
• .* Match 0 or more characters, as many characters as possible (greedy)
• \} Match literal { at the end of line. To make sure you have a proper if line with if followed by something inside parenthesis followed by } at the end.

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You could use the vi( and it'll visualize whatever inside the next parentheses after your cursor, if that's what you mean.