Viml functions

Basics

All vim Functions must start with a captial letter (an underscore is also valid)

function ResizeTabs(size, num, ...)   " (...) indicates accepts *args
    let size = a:size                 " args must be saved to variable in order to be used
    let num = a:num

    let num_extra = a:0               " number of ... args
    let extraA = a:1                  " (...) *args accessed by number
    let extraB = a:2
    return "success"
endfunc

viml functions are cannot be called directly from the vim's command-mode, you must call them using the keyword call

:call ResizeTabs("four", 4, "abc", "efg")

You may also define a command for your function, allowing it to be used without call

command ResizeTabs call ResizeTabs()  " make function into vim-command

:ResizeTabs

See Also viml commands .

Public/Private

vim's version of private-functions are script-local scoped functions. They have a prefix of s:.

function Public()
    " ...
endfunc

function s:Private()
    " ...
endfunc

Parameters

function! PrintArgs(text)
    echo a:text   " arguments are scoped with 'a:...'
endfunc

call PrintArgs("mytext")

You may define a variable number of args (like python's *args using ....

function! VarArgs(name, ...)
    echo a:name

    echo a:0    " number of spread-arguments
    echo a:1    " 1st spread-argument
    echo a:2    " 2nd spread-argument
    echo a:000  " list of all spread-arguments (max 20)
    " ...
endfunc

" pass all spread-args to another function
function! Foo(...)
  echo a:0
endfunc

function! Bar(...)
  call('Foo', a:000)  " <-- expand spread arguments when calling function 'Foo'
endfunc

You can call a function with an array of variable parameters

function! Foo(...)
    echo a:0
endfunction

call Foo("a", "b", "c")       ">> '3'
call call("Foo", ["a", "b", "c"])  ">> '3' -- parameters from array

Visual Selection Range

Both the function and the command need special syntax to properly handle a visual selection range.

function! OrgToMarkdown() range
    echo "firstline num " . a:firstline
    echo "lastline num" . a:lastline
endfunc

command -range OrgToMarkdown <line1>,<line2>:call OrgToMarkdown()

Async

You can schedule background tasks within vim now.
They can be recurring, or scheduled after a period of seconds.

function SayHi(timer)
    echom "hi"
endfunc

let timer = timer_start(2000, 'SayHi')  " in 2s, run 'call SayHi(timer)'

Anonymous Functions

Viml supports lambda expressions.

" define lambda expression
let my_fn = {params -> some_other_function(params)}

" call lambda expression
call my_fn("abc")