How to define a new Vim operator with a parameter?

Question

I have been looking to map a new operator in Vim that takes an extra parameter.

For example, we know that ciw will “cut inside word” and will put you int

Answer 1

Here is an example implementation of the command described in the question, for illustrative purposes.

nnoremap  s :set opfunc=Surroundg@
vnoremap  s :call Surround(visualmode(), 1)

function! Surround(vt, ...)
    let s = InputChar()
    if s =~ "\" || s =~ "\"
        return
    endif
    let [sl, sc] = getpos(a:0 ? "'<" : "'[")[1:2]
    let [el, ec] = getpos(a:0 ? "'>" : "']")[1:2]
    if a:vt == 'line' || a:vt == 'V'
        call append(el, s)
        call append(sl-1, s)
    elseif a:vt == 'block' || a:vt == "\"
        exe sl.','.el 's/\%'.sc.'c\|\%'.ec.'c.\zs/\=s/g|norm!``'
    else
        exe el 's/\%'.ec.'c.\zs/\=s/|norm!``'
        exe sl 's/\%'.sc.'c/\=s/|norm!``'
    endif
endfunction

To get user input, the function InputChar() is used, assuming that the required argument is a single character.

function! InputChar()
    let c = getchar()
    return type(c) == type(0) ? nr2char(c) : c
endfunction

If it is necessary to accept a string argument, change the call to InputChar() in Surround() to the call to input(), instead.