Test string after a pattern

Question

I want to test, if the cursor is currently in a comment line. For example in C it looks like this:

// This is a comment line

now it's also possible that it's a big comment section:

/*
 * Big comment section
 */

Now I'd like to read the current line and look what the first character is. Is there a function where I can compare a regex-pattern with the current line? Like this:

if match(getline(line(".")), "^[/\*]")
    (do something)
endif

but match seems to have another functionality according to the :h match help page. Do you have an idea how I can achieve a "regex-pattern-comparison"?

Answer 1

:h :match is about command, while :h match() is about a function. Make sure you've read and understood :h help-context, :h help-summary and How do I navigate to topics in Vim's documentation? before you move on.

But it's a wrong idea to do your job twice. Whenever is the :syntax on Vim already does its best at source code parsing. This is how to make use of it:

function! IsCursorOn(item) abort
    if !exists('b:current_syntax')
        " really don't know
        return
    endif

    " get syntax ID under cursor
    let l:id = synID(line('.'), col('.'), 1)

    " test if name matches
    return synIDattr(l:id, 'name') =~? a:item
endfunction

:echo IsCursorOn("Comment")

Answer 2

As Matt has said, the correct approach is to test the current syntax type.

In C and C++ case, I test comments with the pattern '\c\vcomment|doxygen'

" autoload/lh/syntax.vim
[...]

function! lh#syntax#match_at(syn_pattern, l, c) abort
  try
    let stack = synstack(a:l, a:c)
    let names = map(stack, 'synIDattr(v:val, "name")')
    let idx = match(names, a:syn_pattern)
    return idx >= 0
  catch /.*/
    throw "Cannot fetch synstack at line:".a:l.", col:".a:c
  endtry
  return 0
endfunction

function! lh#syntax#is_a_comment_at(l,c) abort
  return lh#syntax#match_at('\c\vcomment|doxygen', a:l, a:c)
endfunction