closure in vim script

gistfile11

function! s:foo(num)
    let foo = {'i': a:num}
    function foo.funcall() dict
        let self.i += 1
        return self.i
    endfunction
    return foo
endfunction


echo s:foo(1).funcall()
let s:clos = s:foo(5)
" 6
echo s:clos.funcall()
" 7
echo s:clos.funcall()
" 8
echo s:clos.funcall()