New uesr-defined commands in vim

new-command.vim

" Entry point. Initialize RPC. If it succeeds, then attach commands to the `rpcnotify` invocations.
function! s:connect()
  let id = s:initRpc()
  
  if 0 == id
    echoerr "calculator: cannot start rpc process"
  elseif -1 == id
    echoerr "calculator: rpc process is not executable"
  else
    " Mutate our jobId variable to hold the channel ID
    let s:calculatorJobId = id 
    
    " --- Add the following line --- "
    call s:configureCommands() 
  endif
endfunction


function! s:configureCommands()
  command! -nargs=+ Add :call s:add(<f-args>)
  command! -nargs=+ Multiply :call s:multiply(<f-args>)
endfunction

" Constants for RPC messages.
let s:Add = 'add'
let s:Multiply = 'multiply'

function! s:add(...)
  let s:p = get(a:, 1, 0)
  let s:q = get(a:, 2, 0)

  call rpcnotify(s:calculatorJobId, s:Add, str2nr(s:p), str2nr(s:q))
endfunction

function! s:multiply(...)
  let s:p = get(a:, 1, 1)
  let s:q = get(a:, 2, 1)

  call rpcnotify(s:calculatorJobId, s:Multiply, str2nr(s:p), str2nr(s:q))
endfunction