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4. Automatically loading functions ~
							*autoload-functions*
When using many or large functions, it's possible to automatically define them
only when they are used.  There are two methods: with an autocommand and with
the "autoload" directory in 'runtimepath'.


Using an autocommand ~

This is introduced in the user manual, section |41.14|.

The autocommand is useful if you have a plugin that is a long Vim script file.
You can define the autocommand and quickly quit the script with `:finish`.
That makes Vim startup faster.  The autocommand should then load the same file
again, setting a variable to skip the `:finish` command.

Use the FuncUndefined autocommand event with a pattern that matches the
function(s) to be defined.  Example: >

	:au FuncUndefined BufNet* source ~/vim/bufnetfuncs.vim

The file "~/vim/bufnetfuncs.vim" should then define functions that start with
"BufNet".  Also see |FuncUndefined|.


Using an autoload script ~
							*autoload* *E746*
This is introduced in the user manual, section |41.15|.

Using a script in the "autoload" directory is simpler, but requires using
exactly the right file name.  A function that can be autoloaded has a name
like this: >

	:call filename#funcname()

When such a function is called, and it is not defined yet, Vim will search the
"autoload" directories in 'runtimepath' for a script file called
"filename.vim".  For example "~/.config/nvim/autoload/filename.vim".  That
file should then define the function like this: >

	function filename#funcname()
	   echo "Done!"
	endfunction

If the file doesn't exist, Vim will also search in 'packpath' (under "start")
to allow calling packages' functions from your |vimrc| when the packages have
not been added to 'runtimepath' yet (see |packages|).

The file name and the name used before the # in the function must match
exactly, and the defined function must have the name exactly as it will be
called.

It is possible to use subdirectories.  Every # in the function name works like
a path separator.  Thus when calling a function: >

	:call foo#bar#func()

Vim will look for the file "autoload/foo/bar.vim" in 'runtimepath'.

This also works when reading a variable that has not been set yet: >

	:let l = foo#bar#lvar

However, when the autoload script was already loaded it won't be loaded again
for an unknown variable.

When assigning a value to such a variable nothing special happens.  This can
be used to pass settings to the autoload script before it's loaded: >

	:let foo#bar#toggle = 1
	:call foo#bar#func()

Note that when you make a mistake and call a function that is supposed to be
defined in an autoload script, but the script doesn't actually define the
function, you will get an error message for the missing function.  If you fix
the autoload script it won't be automatically loaded again.  Either restart
Vim or manually source the script.

Also note that if you have two script files, and one calls a function in the
other and vice versa, before the used function is defined, it won't work.
Avoid using the autoload functionality at the toplevel.

Hint: If you distribute a bunch of scripts read |distribute-script|.


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