How to match braces or brackets?

Question

Suppose I want to search for things like

\todo{English sentence}

Then the regex

\\todo{\_.\{-}}

works (I don't know why. I copied it from somewhere long time ago (embarrassed)).

But suppose I want to match things like

\todo{anything whatsoever}

Then the above regex is no good.

For example, if I have

\todo{The problem is caused because of {another} pair of braces inside}

The previous regex just matches

\todo{The problem is caused because of {another}

What is the correct regex, and if possible, can someone break it down a little bit? Things like \_.\{-} already seem to make no sense!

Big thanks.

Answer 1

Per the help pages in Vim:

\{-}    matches 0 or more of the preceding atom, as few as possible
*       Matches 0 or more of the preceding atom, as many as possible.

In my small test case replacing the former with the latter matched your example string. That is:

\\todo{\_.*}

Answer 2

As @LucHermite already mentioned in a comment, regular expressions are not meant for recursive patterns. The solution by @Vitor does not work, as was already confirmed in the comment, because it will match beyond the last } of the \todo command if possible.

Since you did not write anything about what your end goal is, it is difficult to give further concrete tips here. But I would think that you could solve your initial problem e.g. with something like this:

1. Search for \\todo

2. Do vf{ to select up until the first {

3. Do % to increase the selection up until the closing }

If you need some sort of repeated action, you can combine these things with a macro, e.g. qa/\\todo<cr>vf{% ... q where ... is the action you want to perform. Then you can run the macro with @a to repeat.