toggleComment.vim

" toggle comment line

function! SetCommentPrefix()
    let s:comment_prefix = "#"
    if &filetype == "vim"
        " for vim, inline comment start with \"
        let s:comment_prefix = "\""
    elseif &filetype ==? "c" || &filetype ==? "objc" || &filetype ==? "cpp"
        let s:comment_prefix = "//"
    endif
endfunction


function! CommentLine(line_number)
    call SetCommentPrefix()
    " remember current cursor position
    let cpos = getpos(".")
    " move to seletced line
    call setpos(".", [0, a:line_number, 0, 0])
    " just insert comment prefix character at the front of given line
    exec "normal! I".s:comment_prefix 
     "restore cursor position
    call setpos(".", cpos)
endfunction

function! UncommentLine(line_number)
    call SetCommentPrefix()
    " remember current cursor position
    let cpos = getpos(".")
    "move to selected line
    call setpos(".", [0, a:line_number, 0, 0])
    " remove comment prefix charactor
    exec ".s/".escape(s:comment_prefix, s:comment_prefix[0])."//"
    " restore cursor position
    call setpos(".", cpos)
endfunction


function! CheckIsComment(line_number)
    call SetCommentPrefix()
    " check the line for given line number is comment
    let sl = getline(a:line_number)
    let c = 0
    while c < strlen(sl)
        let d = c + strlen(s:comment_prefix) - 1
         "sl[c] is space or tabe?
        if  " \t" =~ sl[c]
            " ignore indentation
            " pass
        elseif sl[(c):(d)] == s:comment_prefix
            return 1
        else
            return 0
        endif
        let c += 1
    endwhile
    return 0
endfunction

function! ToggleCommentLine()
    let cl = line(".")
    if CheckIsComment(cl)
        call UncommentLine(cl)
    else
        call CommentLine(cl)
    endif
endfunction

function! ToggleCommentRange()
    let line_begin = line("'<")
    let line_end = line("'>")
    " decide mode with first line in selection
    let mode_ = CheckIsComment(line_begin)
    let cpos = getpos(".")
    let i = line_begin
    while i < line_end + 1
        if mode_
            call UncommentLine(i)
        else
            call CommentLine(i)
        endif
        let i+=1
    endwhile
endfunction

nnoremap <leader>\ :call ToggleCommentLine()<cr>
vnoremap <leader>\ <esc> :call ToggleCommentRange()<cr>