Replace text and move cursor to end of replacement in insert mode

Question

How can I perform a search-and-replace and leave the cursor at the end of the replacement? I want to replace $...$ with \(...\) as I type in insert mode.

Notice that I can't use an abbreviation, since $ is replaced with two different strings.

The solution I've cobbled together so far is equivalent to:

function Foo()
    let pat = '\$\(.\{-}\)\$'
    if line =~ pat
        execute 's/' . pat . '/\\(\1\\)/'
        call cursor('.', matchend(getline('.'), '\\)'))
    endif
endfunction

inoremap $ $<C-O>:call Foo()<CR>

Is there a better way to do this? The only alternative I found is to add the length of '\\)' to the column number from searchpos, and that isn't any nicer.

Answer 1

One way to get this effect is to instead adaptively enter either \( or \) depending on which is needed. So the first $ will type \( and the second will type \). To figure out which we need, we use searchpairpos, which returns [0,0] when outside the \(..\) pair. Besides being cleaner to code, it is also a bit nicer while typing and works over multiple lines.

function! IDollar()
  let [l:l,l:c] = searchpairpos('\\(', '', '\\)', 'cbWn')
  return l:l ? '\)' : '\('
endfunction

inoremap <silent><expr> $ IDollar()

If you would rather the exact behavior mentioned in your question, here is an improved version of your script. There are a few differences:

1. use setline instead of s/ because there are fewer side-effects,
2. use cursor() since we know the cursor always needs to move forward by 2,
3. use the <c-r>= pattern instead of <c-o> since <c-o> resets the last insert position (useful when backspace does not contain start).

function! Foo()
  let l:pat = '\$\([^\$]\+\)\$'
  let l:line = getline('.')
  if l:line =~ l:pat
    call setline('.', substitute(l:line, l:pat, '\\(\1\\)', ''))
    call cursor(0, col('.')+2)
  endif
  return ''
endfunction
inoremap $ $<c-r>=Foo()<cr>

Answer 2

You can use surround.vim

let g:surround_{char2nr('R')} = "\\(\r\\)"
imap $ $<esc>cs$R`]a

The idea is to create a custom surrounding, "R", which is \(...\). We use this surrounding to replace $...$. Use the '] mark to restart the insert at the end of the changed text.

For more help see:

:h surround-customizing
:h surround-mappings
:h ']
:h char2nr(
:h curly-braces-names