VIM: usr_41

## USR_41

    *usr_41.txt*	For Vim version 9.1.  Last change: 2025 Sep 26

    		     VIM USER MANUAL - by Bram Moolenaar

    			      Write a Vim script

    The Vim script language is used for the startup vimrc file, syntax files, and
    many other things.  This chapter explains the items that can be used in a Vim
    script.  There are a lot of them, therefore this is a long chapter.

    |41.1|	Introduction
    |41.2|	Variables
    |41.3|	Expressions
    |41.4|	Conditionals
    |41.5|	Executing an expression
    |41.6|	Using functions
    |41.7|	Defining a function
    |41.8|	Lists and Dictionaries
    |41.9|	White space
    |41.10|	Line continuation
    |41.11|	Comments
    |41.12|	Fileformat

         Next chapter: |usr_42|  Add new menus
     Previous chapter: |usr_40|  Make new commands
    Table of contents: |usr_toc|

    *41.1*	Introduction				*vim-script-intro* *script*

    Let's start with some nomenclature. A Vim script is any file that Vim can
    interpret and execute.  This includes files written in Vim's scripting
    language like for example .vim files or configuration files like .vimrc and
    .gvimrc.  These scripts may define functions, commands and settings that Vim
    uses to customize and extend its behavior.

    						*vim-script-notation*
    The correct notation is "Vim script" (or "Vim9 script" when refering to the
    new Vim9 language |Vim9-script|), so we will use "Vim script" to refer to the
    Vim scripting language throughout this documentation. This shorthand helps to
    streamline explanations and discussions about scripting with Vim.

    A Vim plugin is a collection of one or more Vim scripts, along with additional
    files like help documentation, configuration files, and other resources,
    designed to add specific features or functionalities to Vim. A plugin can
    provide new commands, enhance existing capabilities, and integrate external
    tools or services into the Vim environment.

    Your first experience with Vim scripts is the vimrc file.  Vim reads it when
    it starts up and executes the commands.  You can set options to the values you
    prefer, define mappings, select plugins and much more.   You can use any colon
    command in it (commands that start with a ":"; these are sometimes referred to
    as Ex commands or command-line commands).

    Syntax files are also Vim scripts.  As are files that set options for a
    specific file type.  A complicated macro can be defined by a separate Vim
    script file.  You can think of other uses yourself.

    Vim script comes in two flavors: legacy and |Vim9|.  Since this help file is
    for new users, we'll teach you the newer and more convenient |Vim9| syntax.
    While legacy script is particularly for Vim, |Vim9| script looks more like
    other languages, such as JavaScript and TypeScript.

    To try out Vim script the best way is to edit a script file and source it.
    Basically:
    	:edit test.vim
    	[insert the script lines you want]
    	:w
    	:source %

    Let's start with a simple example:

    	vim9script
    	var i = 1
    	while i < 5
    	  echo "count is" i
    	  i += 1
    	endwhile

    The output of the example code is:

    	count is 1
    	count is 2
    	count is 3
    	count is 4

    In the first line the `vim9script` command makes clear this is a new, |Vim9|
    script file.  That matters for how the rest of the file is used.  It is
    recommended to put it in the very first line, before any comments.
    							*vim9-declarations*
    The `var i = 1` command declares the "i" variable and initializes it.  The
    generic form is:

    	var {name} = {expression}

    In this case the variable name is "i" and the expression is a simple value,
    the number one.

    The `while` command starts a loop.  The generic form is:

    	while {condition}
    	  {statements}
    	endwhile

    The statements until the matching `endwhile` are executed for as long as the
    condition is true.  The condition used here is the expression "i < 5".  This
    is true when the variable i is smaller than five.
    	Note:
    	If you happen to write a while loop that keeps on running, you can
    	interrupt it by pressing CTRL-C (CTRL-Break on MS-Windows).

    The `echo` command prints its arguments.  In this case the string "count is"
    and the value of the variable i.  Since i is one, this will print:

    	count is 1

    Then there is the `i += 1` command.  This does the same thing as "i = i + 1",
    it adds one to the variable i and assigns the new value to the same variable.

    The example was given to explain the commands, but would you really want to
    make such a loop, it can be written much more compact:

    	for i in range(1, 4)
    	  echo $"count is {i}"
    	endfor

    We won't explain how `for`, `range()` and `$"string"` work until later.
    Follow the links if you are impatient.

    TRYING OUT EXAMPLES

    You can easily try out most examples in these help files without saving the
    commands to a file.  For example, to try out the "for" loop above do this:
    1. position the cursor on the "for"
    2. start Visual mode with "v"
    3. move down to the "endfor"
    4. press colon, then "so" and Enter

    After pressing colon you will see ":'<,'>", which is the range of the Visually
    selected text.

    For some commands it matters they are executed as in |Vim9| script.  But typed
    commands normally use legacy script syntax, such as the example below that
    causes the E1004 error.  For that use this fourth step:
    4. press colon, then "vim9 so" and Enter

    "vim9" is short for `vim9cmd`, which is a command modifier to execute the
    following command in |Vim9| syntax.

    Note that this won't work for examples that require a script context.

    FOUR KINDS OF NUMBERS

    Numbers can be decimal, hexadecimal, octal and binary.

    A hexadecimal number starts with "0x" or "0X".  For example "0x1f" is decimal
    31 and "0x1234" is decimal 4660.

    An octal number starts with "0o", "0O".  "0o17" is decimal 15.

    A binary number starts with "0b" or "0B".  For example "0b101" is decimal 5.

    A decimal number is just digits.  Careful: In legacy script don't put a zero
    before a decimal number, it will be interpreted as an octal number!  That's
    one reason to use |Vim9| script.

    The `echo` command evaluates its argument and when it is a number always
    prints the decimal form.  Example:

    	echo 0x7f 0o36
    	127 30

    A number is made negative with a minus sign.  This also works for hexadecimal,
    octal and binary numbers:

    	echo -0x7f
    	-127

    A minus sign is also used for subtraction.  This can sometimes lead to
    confusion.  If we put a minus sign before both numbers we get an error:

    	echo -0x7f -0o36
    	E1004: White space required before and after '-' at "-0o36"

    Note: if you are not using a |Vim9| script to try out these commands but type
    them directly, they will be executed as legacy script.  Then the echo command
    sees the second minus sign as subtraction.  To get the error, prefix the
    command with `vim9cmd`:

    	vim9cmd echo -0x7f -0o36
    	E1004: White space required before and after '-' at "-0o36"

    White space in an expression is often required to make sure it is easy to read
    and avoid errors.  Such as thinking that the "-0o36" above makes the number
    negative, while it is actually seen as a subtraction.

    To actually have the minus sign be used for negation, you can put the second
    expression in parentheses:

    	echo -0x7f (-0o36)
    	-127 -30

    *41.2*	Variables

    A variable name consists of ASCII letters, digits and the underscore.  It
    cannot start with a digit.  Valid variable names are:

    	counter
    	_aap3
    	very_long_variable_name_with_underscores
    	CamelCaseName
    	LENGTH

    Invalid names are "foo.bar" and "6var".

    Some variables are global.  To see a list of currently defined global
    variables type this command:

    	:let

    You can use global variables everywhere.  However, it is too easy to use the
    same name in two unrelated scripts.  Therefore variables declared in a script
    are local to that script.  For example, if you have this in "script1.vim":

    	vim9script
    	var counter = 5
    	echo counter
    	5

    And you try to use the variable in "script2.vim":

    	vim9script
    	echo counter
    	E121: Undefined variable: counter

    Using a script-local variable means you can be sure that it is only changed in
    that script and not elsewhere.

    If you do want to share variables between scripts, use the "g:" prefix and
    assign the value directly, do not use `var`.  And use a specific name to avoid
    mistakes.  Thus in "script1.vim":

    	vim9script
    	g:mash_counter = 5
    	echo g:mash_counter
    	5

    And then in "script2.vim":

    	vim9script
    	echo g:mash_counter
    	5

    Global variables can also be accessed on the command line, E.g. typing this:
    	echo g:mash_counter
    That will not work for a script-local variable.

    More about script-local variables here: |script-variable|.

    There are more kinds of variables, see |internal-variables|.  The most often
    used ones are:

    	b:name		variable local to a buffer
    	w:name		variable local to a window
    	g:name		global variable (also in a function)
    	v:name		variable predefined by Vim

    DELETING VARIABLES

    Variables take up memory and show up in the output of the `let` command.  To
    delete a global variable use the `unlet` command.  Example:

    	unlet g:counter

    This deletes the global variable "g:counter" to free up the memory it uses.
    If you are not sure if the variable exists, and don't want an error message
    when it doesn't, append !:

    	unlet! g:counter

    You cannot `unlet` script-local variables in |Vim9| script, only in legacy
    script.

    When a script has been processed to the end, the local variables declared
    there will not be deleted.  Functions defined in the script can use them.
    Example:

    	vim9script
    	var counter = 0
    	def g:GetCount(): number
    	  counter += 1
    	  return counter
    	enddef

    Every time you call the function it will return the next count:
    	:echo g:GetCount()
    	1

    	:echo g:GetCount()
    	2

    If you are worried a script-local variable is consuming too much memory, set
    it to an empty or null value after you no longer need it.  Example:
    	var lines = readfile(...)
    	...
    	lines = []

    Note: below we'll leave out the `vim9script` line from examples, so we can
    concentrate on the relevant commands, but you'll still need to put it at the
    top of your script file.

    STRING VARIABLES AND CONSTANTS

    So far only numbers were used for the variable value.  Strings can be used as
    well.  Numbers and strings are the basic types of variables that Vim supports.
    Example:

    	var name = "Peter"
    	echo name
    	Peter

    Every variable has a type.  Very often, as in this example, the type is
    defined by assigning a value.  This is called type inference.  If you do not
    want to give the variable a value yet, you need to specify the type:

    	var name: string
    	var age: number
    	if male
    	   name = "Peter"
    	   age = 42
    	else
    	   name = "Elisa"
    	   age = 45
    	endif

    If you make a mistake and try to assign the wrong type of value you'll get an
    error:

    	age = "Peter"
    	E1012: Type mismatch; expected number but got string

    More about types in |41.8|.

    To assign a string value to a variable, you can use a string constant.  There
    are two types of these.  First the string in double quotes, as we used
    already.  If you want to include a double quote inside the string, put a
    backslash in front of it:

    	var name = "he is \"Peter\""
    	echo name
    	he is "Peter"

    To avoid the need for backslashes, you can use a string in single quotes:

    	var name = 'he is "Peter"'
    	echo name
    	he is "Peter"

    Inside a single-quote string all the characters are as they are.  Only the
    single quote itself is special: you need to use two to get one.  A backslash
    is taken literally, thus you can't use it to change the meaning of the
    character after it:

    	var name = 'P\e''ter'''
    	echo name
    	P\e'ter'

    In double-quote strings it is possible to use special characters.  Here are a
    few useful ones:

    	\t		<Tab>
    	\n		<NL>, line break
    	\r		<CR>, <Enter>
    	\e		<Esc>
    	\b		<BS>, backspace
    	\"		"
    	\\		\, backslash
    	\<Esc>		<Esc>
    	\<C-W>		CTRL-W

    The last two are just examples.  The  "\<name>" form can be used to include
    the special key "name".

    See |expr-quote| for the full list of special items in a string.

    *41.3*	Expressions

    Vim has a fairly standard way to handle expressions.  You can read the
    definition here: |expression-syntax|.  Here we will show the most common
    items.

    The numbers, strings and variables mentioned above are expressions by
    themselves.  Thus everywhere an expression is expected, you can use a number,
    string or variable.  Other basic items in an expression are:

    	$NAME		environment variable
    	&name		option value
    	@r		register contents

    Examples:

    	echo "The value of 'tabstop' is" &ts
    	echo "Your home directory is" $HOME
    	if @a == 'text'

    The &name form can also be used to set an option value, do something and
    restore the old value.  Example:

    	var save_ic = &ic
    	set noic
    	s/The Start/The Beginning/
    	&ic = save_ic

    This makes sure the "The Start" pattern is used with the 'ignorecase' option
    off.  Still, it keeps the value that the user had set.  (Another way to do
    this would be to add "\C" to the pattern, see |/\C|.)

    MATHEMATICS

    It becomes more interesting if we combine these basic items.  Let's start with
    mathematics on numbers:

    	a + b		add
    	a - b		subtract
    	a * b		multiply
    	a / b		divide
    	a % b		modulo

    The usual precedence is used.  Example:

    	echo 10 + 5 * 2
    	20

    Grouping is done with parentheses.  No surprises here.  Example:

    	echo (10 + 5) * 2
    	30

    OTHERS

    Strings can be concatenated with ".." (see |expr6|).  Example:

    	echo "Name: " .. name
    	Name: Peter

    When the "echo" command gets multiple arguments, it separates them with a
    space.  In the example the argument is a single expression, thus no space is
    inserted.

    If you don't like the concatenation you can use the $"string" form, which
    accepts an expression in curly braces:
    	echo $"Name: {name}"

    See |interpolated-string| for more information.

    Borrowed from the C language is the conditional expression:

    	a ? b : c

    If "a" evaluates to true "b" is used, otherwise "c" is used.  Example:

    	var nr = 4
    	echo nr > 5 ? "nr is big" : "nr is small"
    	nr is small

    The three parts of the constructs are always evaluated first, thus you could
    see it works as:

    	(a) ? (b) : (c)

    There is also the falsy operator:
    	echo name ?? "No name given"
    See |??|.

    *41.4*	Conditionals

    The `if` commands executes the following statements, until the matching
    `endif`, only when a condition is met.  The generic form is:

    	if {condition}
    	   {statements}
    	endif

    Only when the expression {condition} evaluates to true or one will the
    {statements} be executed.  If they are not executed they must still be valid
    commands.  If they contain garbage, Vim won't be able to find the matching
    `endif`.

    You can also use `else`.  The generic form for this is:

    	if {condition}
    	   {statements}
    	else
    	   {statements}
    	endif

    The second {statements} block is only executed if the first one isn't.

    Finally, there is `elseif`

    	if {condition}
    	   {statements}
    	elseif {condition}
    	   {statements}
    	endif

    This works just like using `else` and then `if`, but without the need for an
    extra `endif`.

    A useful example for your vimrc file is checking the 'term' option and doing
    something depending upon its value:

    	if &term == "xterm"
    	  # Do stuff for xterm
    	elseif &term == "vt100"
    	  # Do stuff for a vt100 terminal
    	else
    	  # Do something for other terminals
    	endif

    This uses "#" to start a comment, more about that later.

    LOGIC OPERATIONS

    We already used some of them in the examples.  These are the most often used
    ones:

    	a == b		equal to
    	a != b		not equal to
    	a >  b		greater than
    	a >= b		greater than or equal to
    	a <  b		less than
    	a <= b		less than or equal to

    The result is true if the condition is met and false otherwise.  An example:

    	if v:version >= 800
    	  echo "congratulations"
    	else
    	  echo "you are using an old version, upgrade!"
    	endif

    Here "v:version" is a variable defined by Vim, which has the value of the Vim
    version.  800 is for version 8.0, version 8.1 has the value 801.  This is
    useful to write a script that works with multiple versions of Vim.
    See |v:version|.  You can also check for a specific feature with `has()` or a
    specific patch, see |has-patch|.

    The logic operators work both for numbers and strings.  When comparing two
    strings, the mathematical difference is used.  This compares byte values,
    which may not be right for some languages.

    If you try to compare a string with a number you will get an error.

    For strings there are two more useful items:

    	str =~ pat		matches with
    	str !~ pat		does not match with

    The left item "str" is used as a string.  The right item "pat" is used as a
    pattern, like what's used for searching.  Example:

    	if str =~ " "
    	  echo "str contains a space"
    	endif
    	if str !~ '\.$'
    	  echo "str does not end in a full stop"
    	endif

    Notice the use of a single-quote string for the pattern.  This is useful,
    because patterns tend to contain many backslashes and backslashes need to be
    doubled in a double-quote string.

    The match is not anchored, if you want to match the whole string start with
    "^" and end with "$".

    The 'ignorecase' option is not used when comparing strings.  When you do want
    to ignore case append "?".  Thus "==?" compares two strings to be equal while
    ignoring case.  For the full table see |expr-==|.

    MORE LOOPING

    The `while` command was already mentioned.  Two more statements can be used in
    between the `while` and the `endwhile`:

    	continue		Jump back to the start of the while loop; the
    				loop continues.
    	break			Jump forward to the `endwhile`; the loop is
    				discontinued.

    Example:

    	var counter = 1
    	while counter < 40
    	  if skip_number(counter)
    	    continue
    	  endif
    	  if last_number(counter)
    	    break
    	  endif
    	  sleep 50m
    	  ++counter
    	endwhile

    The `sleep` command makes Vim take a nap.  The "50m" specifies fifty
    milliseconds.  Another example is `sleep 4`, which sleeps for four seconds.

    `continue` and `break` can also be used in between `for` and `endfor`.
    Even more looping can be done with the `for` command, see below in |41.8|.

    *41.5*	Executing an expression

    So far the commands in the script were executed by Vim directly.  The
    `execute` command allows executing the result of an expression.  This is a
    very powerful way to build commands and execute them.

    An example is to jump to a tag, which is contained in a variable:

    	execute "tag " .. tag_name

    The ".." is used to concatenate the string "tag " with the value of variable
    "tag_name".  Suppose "tag_name" has the value "get_cmd", then the command that
    will be executed is:

    	tag get_cmd

    The `execute` command can only execute Ex commands.  The `normal` command
    executes Normal mode commands.  However, its argument is not an expression but
    the literal command characters.  Example:

    	normal gg=G

    This jumps to the first line with "gg" and formats all lines with the "="
    operator and the "G" movement.

    To make `normal` work with an expression, combine `execute` with it.
    Example:

    	execute "normal " .. count .. "j"

    This will move the cursor "count" lines down.

    Make sure that the argument for `normal` is a complete command.  Otherwise
    Vim will run into the end of the argument and silently abort the command.  For
    example, if you start the delete operator, you must give the movement command
    also.  This works:

    	normal d$

    This does nothing:

    	normal d

    If you start Insert mode and do not end it with Esc, it will end anyway.  This
    works to insert "new text":

    	execute "normal inew text"

    If you want to do something after inserting text you do need to end Insert
    mode:

    	execute "normal inew text\<Esc>b"

    This inserts "new text" and puts the cursor on the first letter of "text".
    Notice the use of the special key "\<Esc>".  This avoids having to enter a
    real <Esc> character in your script.  That is where `execute` with a
    double-quote string comes in handy.

    If you don't want to execute a string as a command but evaluate it to get the
    result of the expression, you can use the eval() function:

    	var optname = "path"
    	var optvalue = eval('&' .. optname)

    A "&" character is prepended to "path", thus the argument to eval() is
    "&path".  The result will then be the value of the 'path' option.

    *41.6*	Using functions

    Vim defines many functions and provides a large amount of functionality that
    way.  A few examples will be given in this section.  You can find the whole
    list below: |function-list|.

    A function is called with the parameters in between parentheses, separated by
    commas.  Example:

    	search("Date: ", "W")

    This calls the search() function, with arguments "Date: " and "W".  The
    search() function uses its first argument as a search pattern and the second
    one as flags.  The "W" flag means the search doesn't wrap around the end of
    the file.

    Using the `call` command is optional in |Vim9| script.  It is required in
    legacy script and on the command line:

    	call search("Date: ", "W")

    A function can be called in an expression.  Example:

    	var line = getline(".")
    	var repl = substitute(line, '\a', "*", "g")
    	setline(".", repl)

    The getline() function obtains a line from the current buffer.  Its argument
    is a specification of the line number.  In this case "." is used, which means
    the line where the cursor is.

    The substitute() function does something similar to the `:substitute` command.
    The first argument "line" is the string on which to perform the substitution.
    The second argument '\a' is the pattern, the third "*" is the replacement
    string.  Finally, the last argument "g" is the flags.

    The setline() function sets the line, specified by the first argument, to a
    new string, the second argument.  In this example the line under the cursor is
    replaced with the result of the substitute().  Thus the effect of the three
    statements is equal to:

    	:substitute/\a/*/g

    Using the functions becomes interesting when you do more work before and
    after the substitute() call.

    FUNCTIONS						*function-list*

    There are many functions.  We will mention them here, grouped by what they are
    used for.  You can find an alphabetical list here: |builtin-function-list|.
    Use CTRL-] on the function name to jump to detailed help on it.

    String manipulation:					*string-functions*
    	nr2char()		get a character by its number value
    	list2str()		get a character string from a list of numbers
    	char2nr()		get number value of a character
    	str2list()		get list of numbers from a string
    	str2nr()		convert a string to a Number
    	str2float()		convert a string to a Float
    	printf()		format a string according to "%" items
    	escape()		escape characters in a string with a '\'
    	shellescape()		escape a string for use with a shell command
    	fnameescape()		escape a file name for use with a Vim command
    	tr()			translate characters from one set to another
    	strtrans()		translate a string to make it printable
    	keytrans()		translate internal keycodes to a form that
    				can be used by |:map|
    	tolower()		turn a string to lowercase
    	toupper()		turn a string to uppercase
    	charclass()		class of a character
    	match()			position where a pattern matches in a string
    	matchbufline()		all the matches of a pattern in a buffer
    	matchend()		position where a pattern match ends in a string
    	matchfuzzy()		fuzzy matches a string in a list of strings
    	matchfuzzypos()		fuzzy matches a string in a list of strings
    	matchstr()		match of a pattern in a string
    	matchstrlist()		all the matches of a pattern in a List of
    				strings
    	matchstrpos()		match and positions of a pattern in a string
    	matchlist()		like matchstr() and also return submatches
    	stridx()		first index of a short string in a long string
    	strridx()		last index of a short string in a long string
    	strlen()		length of a string in bytes
    	strcharlen()		length of a string in characters
    	strchars()		number of characters in a string
    	strutf16len()		number of UTF-16 code units in a string
    	strwidth()		size of string when displayed
    	strdisplaywidth()	size of string when displayed, deals with tabs
    	setcellwidths()		set character cell width overrides
    	getcellwidths()		get character cell width overrides
    	getcellpixels()		get character cell pixel size
    	reverse()		reverse the order of characters in a string
    	substitute()		substitute a pattern match with a string
    	submatch()		get a specific match in ":s" and substitute()
    	strpart()		get part of a string using byte index
    	strcharpart()		get part of a string using char index
    	slice()			take a slice of a string, using char index in
    				Vim9 script
    	strgetchar()		get character from a string using char index
    	expand()		expand special keywords
    	expandcmd()		expand a command like done for `:edit`
    	iconv()			convert text from one encoding to another
    	byteidx()		byte index of a character in a string
    	byteidxcomp()		like byteidx() but count composing characters
    	charidx()		character index of a byte in a string
    	utf16idx()		UTF-16 index of a byte in a string
    	repeat()		repeat a string multiple times
    	eval()			evaluate a string expression
    	execute()		execute an Ex command and get the output
    	win_execute()		like execute() but in a specified window
    	trim()			trim characters from a string
    	bindtextdomain()	set message lookup translation base path
    	gettext()		lookup message translation
    	ngettext()		lookup single/plural message translation
    	str2blob()		convert a list of strings into a blob
    	blob2str()		convert a blob into a list of strings
    	items()			get List of String index-character pairs
    	uri_encode()		URI-encode a string
    	uri_decode()		URI-decode a string

    List manipulation:					*list-functions*
    	get()			get an item without error for wrong index
    	len()			number of items in a List
    	empty()			check if List is empty
    	insert()		insert an item somewhere in a List
    	add()			append an item to a List
    	extend()		append a List to a List
    	extendnew()		make a new List and append items
    	remove()		remove one or more items from a List
    	copy()			make a shallow copy of a List
    	deepcopy()		make a full copy of a List
    	filter()		remove selected items from a List
    	map()			change each List item
    	mapnew()		make a new List with changed items
    	foreach()		apply function to List items
    	reduce()		reduce a List to a value
    	slice()			take a slice of a List
    	sort()			sort a List
    	reverse()		reverse the order of items in a List
    	uniq()			remove copies of repeated adjacent items
    	split()			split a String into a List
    	join()			join List items into a String
    	range()			return a List with a sequence of numbers
    	string()		String representation of a List
    	call()			call a function with List as arguments
    	index()			index of a value in a List
    	indexof()		index in a List where an expression is true
    	max()			maximum value in a List
    	min()			minimum value in a List
    	count()			count number of times a value appears in a List
    	repeat()		repeat a List multiple times
    	flatten()		flatten a List
    	flattennew()		flatten a copy of a List
    	items()			get List of List index-value pairs

    Tuple manipulation:					*tuple-functions*
    	copy()			make a shallow copy of a Tuple
    	count()			count number of times a value appears in a
    				Tuple
    	deepcopy()		make a full copy of a Tuple
    	empty()			check if Tuple is empty
    	foreach()		apply function to Tuple items
    	get()			get an item without error for wrong index
    	index()			index of a value in a Tuple
    	indexof()		index in a Tuple where an expression is true
    	items()			get List of Tuple index-value pairs
    	join()			join Tuple items into a String
    	len()			number of items in a Tuple
    	list2tuple()		convert a list of items into a Tuple
    	max()			maximum value in a Tuple
    	min()			minimum value in a Tuple
    	reduce()		reduce a Tuple to a value
    	repeat()		repeat a Tuple multiple times
    	reverse()		reverse the order of items in a Tuple
    	slice()			take a slice of a Tuple
    	string()		string representation of a Tuple
    	tuple2list()		convert a Tuple into a List

    Dictionary manipulation:				*dict-functions*
    	get()			get an entry without an error for a wrong key
    	len()			number of entries in a Dictionary
    	has_key()		check whether a key appears in a Dictionary
    	empty()			check if Dictionary is empty
    	remove()		remove an entry from a Dictionary
    	extend()		add entries from one Dictionary to another
    	extendnew()		make a new Dictionary and append items
    	filter()		remove selected entries from a Dictionary
    	map()			change each Dictionary entry
    	mapnew()		make a new Dictionary with changed items
    	foreach()		apply function to Dictionary items
    	keys()			get List of Dictionary keys
    	values()		get List of Dictionary values
    	items()			get List of Dictionary key-value pairs
    	copy()			make a shallow copy of a Dictionary
    	deepcopy()		make a full copy of a Dictionary
    	string()		String representation of a Dictionary
    	max()			maximum value in a Dictionary
    	min()			minimum value in a Dictionary
    	count()			count number of times a value appears

    Floating point computation:				*float-functions*
    	float2nr()		convert Float to Number
    	abs()			absolute value (also works for Number)
    	round()			round off
    	ceil()			round up
    	floor()			round down
    	trunc()			remove value after decimal point
    	fmod()			remainder of division
    	exp()			exponential
    	log()			natural logarithm (logarithm to base e)
    	log10()			logarithm to base 10
    	pow()			value of x to the exponent y
    	sqrt()			square root
    	sin()			sine
    	cos()			cosine
    	tan()			tangent
    	asin()			arc sine
    	acos()			arc cosine
    	atan()			arc tangent
    	atan2()			arc tangent
    	sinh()			hyperbolic sine
    	cosh()			hyperbolic cosine
    	tanh()			hyperbolic tangent
    	isinf()			check for infinity
    	isnan()			check for not a number

    Blob manipulation:					*blob-functions*
    	blob2list()		get a list of numbers from a blob
    	list2blob()		get a blob from a list of numbers
    	reverse()		reverse the order of numbers in a blob
    	index()			index of a value in a Blob
    	indexof()		index in a Blob where an expression is true
    	items()			get List of Blob index-value pairs

    Other computation:					*bitwise-function*
    	and()			bitwise AND
    	invert()		bitwise invert
    	or()			bitwise OR
    	xor()			bitwise XOR
    	sha256()		SHA-256 hash
    	rand()			get a pseudo-random number
    	srand()			initialize seed used by rand()

    Variables:						*var-functions*
    	instanceof()		check if a variable is an instance of a given
    				class
    	type()			type of a variable as a number
    	typename()		type of a variable as text
    	islocked()		check if a variable is locked
    	funcref()		get a Funcref for a function reference
    	function()		get a Funcref for a function name
    	getbufvar()		get a variable value from a specific buffer
    	setbufvar()		set a variable in a specific buffer
    	getwinvar()		get a variable from specific window
    	gettabvar()		get a variable from specific tab page
    	gettabwinvar()		get a variable from specific window & tab page
    	setwinvar()		set a variable in a specific window
    	settabvar()		set a variable in a specific tab page
    	settabwinvar()		set a variable in a specific window & tab page
    	garbagecollect()	possibly free memory

    Cursor and mark position:		*cursor-functions* *mark-functions*
    	col()			column number of the cursor or a mark
    	virtcol()		screen column of the cursor or a mark
    	line()			line number of the cursor or mark
    	wincol()		window column number of the cursor
    	winline()		window line number of the cursor
    	cursor()		position the cursor at a line/column
    	screencol()		get screen column of the cursor
    	screenrow()		get screen row of the cursor
    	screenpos()		screen row and col of a text character
    	virtcol2col()		byte index of a text character on screen
    	getcurpos()		get position of the cursor
    	getpos()		get position of cursor, mark, etc.
    	setpos()		set position of cursor, mark, etc.
    	getmarklist()		list of global/local marks
    	byte2line()		get line number at a specific byte count
    	line2byte()		byte count at a specific line
    	diff_filler()		get the number of filler lines above a line
    	screenattr()		get attribute at a screen line/row
    	screenchar()		get character code at a screen line/row
    	screenchars()		get character codes at a screen line/row
    	screenstring()		get string of characters at a screen line/row
    	charcol()		character number of the cursor or a mark
    	getcharpos()		get character position of cursor, mark, etc.
    	setcharpos()		set character position of cursor, mark, etc.
    	getcursorcharpos()	get character position of the cursor
    	setcursorcharpos()	set character position of the cursor

    Working with text in the current buffer:		*text-functions*
    	getline()		get a line or list of lines from the buffer
    	getregion()		get a region of text from the buffer
    	getregionpos()		get a list of positions for a region
    	setline()		replace a line in the buffer
    	append()		append line or list of lines in the buffer
    	indent()		indent of a specific line
    	cindent()		indent according to C indenting
    	lispindent()		indent according to Lisp indenting
    	nextnonblank()		find next non-blank line
    	prevnonblank()		find previous non-blank line
    	search()		find a match for a pattern
    	searchpos()		find a match for a pattern
    	searchcount()		get number of matches before/after the cursor
    	searchpair()		find the other end of a start/skip/end
    	searchpairpos()		find the other end of a start/skip/end
    	searchdecl()		search for the declaration of a name
    	getcharsearch()		return character search information
    	setcharsearch()		set character search information

    Working with text in another buffer:
    	getbufline()		get a list of lines from the specified buffer
    	getbufoneline()		get a one line from the specified buffer
    	setbufline()		replace a line in the specified buffer
    	appendbufline()		append a list of lines in the specified buffer
    	deletebufline()		delete lines from a specified buffer

    					*system-functions* *file-functions*
    System functions and manipulation of files:
    	glob()			expand wildcards
    	globpath()		expand wildcards in a number of directories
    	glob2regpat()		convert a glob pattern into a search pattern
    	findfile()		find a file in a list of directories
    	finddir()		find a directory in a list of directories
    	resolve()		find out where a shortcut points to
    	fnamemodify()		modify a file name
    	pathshorten()		shorten directory names in a path
    	simplify()		simplify a path without changing its meaning
    	executable()		check if an executable program exists
    	exepath()		full path of an executable program
    	filereadable()		check if a file can be read
    	filewritable()		check if a file can be written to
    	getfperm()		get the permissions of a file
    	setfperm()		set the permissions of a file
    	getftype()		get the kind of a file
    	isabsolutepath()	check if a path is absolute
    	isdirectory()		check if a directory exists
    	getfsize()		get the size of a file
    	getcwd()		get the current working directory
    	haslocaldir()		check if current window used |:lcd| or |:tcd|
    	tempname()		get the name of a temporary file
    	mkdir()			create a new directory
    	chdir()			change current working directory
    	delete()		delete a file
    	rename()		rename a file
    	system()		get the result of a shell command as a string
    	systemlist()		get the result of a shell command as a list
    	environ()		get all environment variables
    	getenv()		get one environment variable
    	setenv()		set an environment variable
    	hostname()		name of the system
    	readfile()		read a file into a List of lines
    	readblob()		read a file into a Blob
    	readdir()		get a List of file names in a directory
    	readdirex()		get a List of file information in a directory
    	writefile()		write a List of lines or Blob into a file
    	filecopy()		copy a file {from} to {to}

    Date and Time:				*date-functions* *time-functions*
    	getftime()		get last modification time of a file
    	localtime()		get current time in seconds
    	strftime()		convert time to a string
    	strptime()		convert a date/time string to time
    	reltime()		get the current or elapsed time accurately
    	reltimestr()		convert reltime() result to a string
    	reltimefloat()		convert reltime() result to a Float

    Autocmds:					*autocmd-functions*
    	autocmd_add()		add a list of autocmds and groups
    	autocmd_delete()	delete a list of autocmds and groups
    	autocmd_get()		return a list of autocmds

    			*buffer-functions* *window-functions* *arg-functions*
    Buffers, windows and the argument list:
    	argc()			number of entries in the argument list
    	argidx()		current position in the argument list
    	arglistid()		get id of the argument list
    	argv()			get one entry from the argument list
    	bufadd()		add a file to the list of buffers
    	bufexists()		check if a buffer exists
    	buflisted()		check if a buffer exists and is listed
    	bufload()		ensure a buffer is loaded
    	bufloaded()		check if a buffer exists and is loaded
    	bufname()		get the name of a specific buffer
    	bufnr()			get the buffer number of a specific buffer
    	tabpagebuflist()	return List of buffers in a tab page
    	tabpagenr()		get the number of a tab page
    	tabpagewinnr()		like winnr() for a specified tab page
    	winnr()			get the window number for the current window
    	bufwinid()		get the window ID of a specific buffer
    	bufwinnr()		get the window number of a specific buffer
    	winbufnr()		get the buffer number of a specific window
    	listener_add()		add a callback to listen to changes
    	listener_flush()	invoke listener callbacks
    	listener_remove()	remove a listener callback
    	win_findbuf()		find windows containing a buffer
    	win_getid()		get window ID of a window
    	win_gettype()		get type of window
    	win_gotoid()		go to window with ID
    	win_id2tabwin()		get tab and window nr from window ID
    	win_id2win()		get window nr from window ID
    	win_move_separator()	move window vertical separator
    	win_move_statusline()	move window status line
    	win_splitmove()		move window to a split of another window
    	getbufinfo()		get a list with buffer information
    	gettabinfo()		get a list with tab page information
    	getwininfo()		get a list with window information
    	getchangelist()		get a list of change list entries
    	getjumplist()		get a list of jump list entries
    	swapfilelist()		list of existing swap files in 'directory'
    	swapinfo()		information about a swap file
    	swapname()		get the swap file path of a buffer

    Command line:					*command-line-functions*
    	getcmdcomplpat()	get completion pattern of the current command
    				line
    	getcmdcompltype()	get the type of the current command line
    				completion
    	getcmdline()		get the current command line input
    	getcmdprompt()		get the current command line prompt
    	getcmdpos()		get position of the cursor in the command line
    	getcmdscreenpos()	get screen position of the cursor in the
    				command line
    	setcmdline()		set the current command line
    	setcmdpos()		set position of the cursor in the command line
    	getcmdtype()		return the current command-line type
    	getcmdwintype()		return the current command-line window type
    	getcompletion()		list of command-line completion matches
    	getcompletiontype()	get the type of the command-line completion
    				for specified string
    	fullcommand()		get full command name
    	cmdcomplete_info()	get command-line completion information

    Quickfix and location lists:			*quickfix-functions*
    	getqflist()		list of quickfix errors
    	setqflist()		modify a quickfix list
    	getloclist()		list of location list items
    	setloclist()		modify a location list

    Insert mode completion:				*completion-functions*
    	complete()		set found matches
    	complete_add()		add to found matches
    	complete_check()	check if completion should be aborted
    	complete_info()		get current completion information
    	complete_match()	get insert completion start match col and
    				trigger text
    	preinserted()		check if text is inserted after cursor
    	pumvisible()		check if the popup menu is displayed
    	pum_getpos()		position and size of popup menu if visible

    Folding:					*folding-functions*
    	foldclosed()		check for a closed fold at a specific line
    	foldclosedend()		like foldclosed() but return the last line
    	foldlevel()		check for the fold level at a specific line
    	foldtext()		generate the line displayed for a closed fold
    	foldtextresult()	get the text displayed for a closed fold

    Syntax and highlighting:	  *syntax-functions* *highlighting-functions*
    	clearmatches()		clear all matches defined by |matchadd()| and
    				the |:match| commands
    	getmatches()		get all matches defined by |matchadd()| and
    				the |:match| commands
    	hlexists()		check if a highlight group exists
    	hlget()			get highlight group attributes
    	hlset()			set highlight group attributes
    	hlID()			get ID of a highlight group
    	synID()			get syntax ID at a specific position
    	synIDattr()		get a specific attribute of a syntax ID
    	synIDtrans()		get translated syntax ID
    	synstack()		get list of syntax IDs at a specific position
    	synconcealed()		get info about (syntax) concealing
    	diff_hlID()		get highlight ID for diff mode at a position
    	matchadd()		define a pattern to highlight (a "match")
    	matchaddpos()		define a list of positions to highlight
    	matcharg()		get info about |:match| arguments
    	matchdelete()		delete a match defined by |matchadd()| or a
    				|:match| command
    	setmatches()		restore a list of matches saved by
    				|getmatches()|

    Spelling:					*spell-functions*
    	spellbadword()		locate badly spelled word at or after cursor
    	spellsuggest()		return suggested spelling corrections
    	soundfold()		return the sound-a-like equivalent of a word

    History:					*history-functions*
    	histadd()		add an item to a history
    	histdel()		delete an item from a history
    	histget()		get an item from a history
    	histnr()		get highest index of a history list

    Interactive:					*interactive-functions*
    	browse()		put up a file requester
    	browsedir()		put up a directory requester
    	confirm()		let the user make a choice
    	getchar()		get a character from the user
    	getcharstr()		get a character from the user as a string
    	getcharmod()		get modifiers for the last typed character
    	getmousepos()		get last known mouse position
    	getmouseshape()		get name of the current mouse shape
    	echoraw()		output characters as-is
    	feedkeys()		put characters in the typeahead queue
    	input()			get a line from the user
    	inputlist()		let the user pick an entry from a list
    	inputsecret()		get a line from the user without showing it
    	inputdialog()		get a line from the user in a dialog
    	inputsave()		save and clear typeahead
    	inputrestore()		restore typeahead

    GUI:						*gui-functions*
    	getfontname()		get name of current font being used
    	getwinpos()		position of the Vim window
    	getwinposx()		X position of the Vim window
    	getwinposy()		Y position of the Vim window
    	balloon_show()		set the balloon content
    	balloon_split()		split a message for a balloon
    	balloon_gettext()	get the text in the balloon

    Vim server:					*server-functions*
    	serverlist()		return the list of server names
    	remote_startserver()	run a server
    	remote_send()		send command characters to a Vim server
    	remote_expr()		evaluate an expression in a Vim server
    	server2client()		send a reply to a client of a Vim server
    	remote_peek()		check if there is a reply from a Vim server
    	remote_read()		read a reply from a Vim server
    	foreground()		move the Vim window to the foreground
    	remote_foreground()	move the Vim server window to the foreground

    Window size and position:			*window-size-functions*
    	winheight()		get height of a specific window
    	winwidth()		get width of a specific window
    	win_screenpos()		get screen position of a window
    	winlayout()		get layout of windows in a tab page
    	winrestcmd()		return command to restore window sizes
    	winsaveview()		get view of current window
    	winrestview()		restore saved view of current window

    Mappings and Menus:			    *mapping-functions*
    	digraph_get()		get |digraph|
    	digraph_getlist()	get all |digraph|s
    	digraph_set()		register |digraph|
    	digraph_setlist()	register multiple |digraph|s
    	hasmapto()		check if a mapping exists
    	mapcheck()		check if a matching mapping exists
    	maparg()		get rhs of a mapping
    	maplist()		get list of all mappings
    	mapset()		restore a mapping
    	menu_info()		get information about a menu item
    	wildmenumode()		check if the wildmode is active
    	wildtrigger()		start wildcard expansion

    Testing:				    *test-functions*
    	assert_equal()		assert that two expressions values are equal
    	assert_equalfile()	assert that two file contents are equal
    	assert_notequal()	assert that two expressions values are not equal
    	assert_inrange()	assert that an expression is inside a range
    	assert_match()		assert that a pattern matches the value
    	assert_notmatch()	assert that a pattern does not match the value
    	assert_false()		assert that an expression is false
    	assert_true()		assert that an expression is true
    	assert_exception()	assert that a command throws an exception
    	assert_beeps()		assert that a command beeps
    	assert_nobeep()		assert that a command does not cause a beep
    	assert_fails()		assert that a command fails
    	assert_report()		report a test failure
    	test_alloc_fail()	make memory allocation fail
    	test_autochdir()	enable 'autochdir' during startup
    	test_override()		test with Vim internal overrides
    	test_garbagecollect_now()   free memory right now
    	test_garbagecollect_soon()  set a flag to free memory soon
    	test_getvalue()		get value of an internal variable
    	test_gui_event()	generate a GUI event for testing
    	test_ignore_error()	ignore a specific error message
    	test_mswin_event()	generate an MS-Windows event
    	test_null_blob()	return a null Blob
    	test_null_channel()	return a null Channel
    	test_null_dict()	return a null Dict
    	test_null_function()	return a null Funcref
    	test_null_job()		return a null Job
    	test_null_list()	return a null List
    	test_null_partial()	return a null Partial function
    	test_null_string()	return a null String
    	test_null_tuple()	return a null Tuple
    	test_settime()		set the time Vim uses internally
    	test_setmouse()		set the mouse position
    	test_feedinput()	add key sequence to input buffer
    	test_option_not_set()	reset flag indicating option was set
    	test_refcount()		return an expression's reference count
    	test_srand_seed()	set the seed value for srand()
    	test_unknown()		return a value with unknown type
    	test_void()		return a value with void type

    Inter-process communication:		    *channel-functions*
    	ch_canread()		check if there is something to read
    	ch_open()		open a channel
    	ch_close()		close a channel
    	ch_close_in()		close the in part of a channel
    	ch_read()		read a message from a channel
    	ch_readblob()		read a Blob from a channel
    	ch_readraw()		read a raw message from a channel
    	ch_sendexpr()		send a JSON message over a channel
    	ch_sendraw()		send a raw message over a channel
    	ch_evalexpr()		evaluate an expression over channel
    	ch_evalraw()		evaluate a raw string over channel
    	ch_status()		get status of a channel
    	ch_getbufnr()		get the buffer number of a channel
    	ch_getjob()		get the job associated with a channel
    	ch_info()		get channel information
    	ch_log()		write a message in the channel log file
    	ch_logfile()		set the channel log file
    	ch_setoptions()		set the options for a channel
    	json_encode()		encode an expression to a JSON string
    	json_decode()		decode a JSON string to Vim types
    	js_encode()		encode an expression to a JSON string
    	js_decode()		decode a JSON string to Vim types
    	base64_encode()		encode a blob into a base64 string
    	base64_decode()		decode a base64 string into a blob
    	err_teapot()		give error 418 or 503

    Jobs:						*job-functions*
    	job_start()		start a job
    	job_stop()		stop a job
    	job_status()		get the status of a job
    	job_getchannel()	get the channel used by a job
    	job_info()		get information about a job
    	job_setoptions()	set options for a job

    Signs:						*sign-functions*
    	sign_define()		define or update a sign
    	sign_getdefined()	get a list of defined signs
    	sign_getplaced()	get a list of placed signs
    	sign_jump()		jump to a sign
    	sign_place()		place a sign
    	sign_placelist()	place a list of signs
    	sign_undefine()		undefine a sign
    	sign_unplace()		unplace a sign
    	sign_unplacelist()	unplace a list of signs

    Terminal window:				*terminal-functions*
    	term_start()		open a terminal window and run a job
    	term_list()		get the list of terminal buffers
    	term_sendkeys()		send keystrokes to a terminal
    	term_wait()		wait for screen to be updated
    	term_getjob()		get the job associated with a terminal
    	term_scrape()		get row of a terminal screen
    	term_getline()		get a line of text from a terminal
    	term_getattr()		get the value of attribute {what}
    	term_getcursor()	get the cursor position of a terminal
    	term_getscrolled()	get the scroll count of a terminal
    	term_getaltscreen()	get the alternate screen flag
    	term_getsize()		get the size of a terminal
    	term_getstatus()	get the status of a terminal
    	term_gettitle()		get the title of a terminal
    	term_gettty()		get the tty name of a terminal
    	term_setansicolors()	set 16 ANSI colors, used for GUI
    	term_getansicolors()	get 16 ANSI colors, used for GUI
    	term_dumpdiff()		display difference between two screen dumps
    	term_dumpload()		load a terminal screen dump in a window
    	term_dumpwrite()	dump contents of a terminal screen to a file
    	term_setkill()		set signal to stop job in a terminal
    	term_setrestore()	set command to restore a terminal
    	term_setsize()		set the size of a terminal
    	term_setapi()		set terminal JSON API function name prefix

    Popup window:					*popup-window-functions*
    	popup_create()		create popup centered in the screen
    	popup_atcursor()	create popup just above the cursor position,
    				closes when the cursor moves away
    	popup_beval()		at the position indicated by v:beval_
    				variables, closes when the mouse moves away
    	popup_notification()	show a notification for three seconds
    	popup_dialog()		create popup centered with padding and border
    	popup_menu()		prompt for selecting an item from a list
    	popup_hide()		hide a popup temporarily
    	popup_show()		show a previously hidden popup
    	popup_move()		change the position and size of a popup
    	popup_setoptions()	override options of a popup
    	popup_settext()		replace the popup buffer contents
    	popup_setbuf()		set the popup buffer
    	popup_close()		close one popup
    	popup_clear()		close all popups
    	popup_filter_menu()	select from a list of items
    	popup_filter_yesno()	block until 'y' or 'n' is pressed
    	popup_getoptions()	get current options for a popup
    	popup_getpos()		get actual position and size of a popup
    	popup_findecho()	get window ID for popup used for `:echowindow`
    	popup_findinfo()	get window ID for popup info window
    	popup_findpreview()	get window ID for popup preview window
    	popup_list()		get list of all popup window IDs
    	popup_locate()		get popup window ID from its screen position

    Timers:						*timer-functions*
    	timer_start()		create a timer
    	timer_pause()		pause or unpause a timer
    	timer_stop()		stop a timer
    	timer_stopall()		stop all timers
    	timer_info()		get information about timers

    Tags:						*tag-functions*
    	taglist()		get list of matching tags
    	tagfiles()		get a list of tags files
    	gettagstack()		get the tag stack of a window
    	settagstack()		modify the tag stack of a window

    Prompt Buffer:					*promptbuffer-functions*
    	prompt_getprompt()	get the effective prompt text for a buffer
    	prompt_setcallback()	set prompt callback for a buffer
    	prompt_setinterrupt()	set interrupt callback for a buffer
    	prompt_setprompt()	set the prompt text for a buffer

    Registers:					*register-functions*
    	getreg()		get contents of a register
    	getreginfo()		get information about a register
    	getregtype()		get type of a register
    	setreg()		set contents and type of a register
    	reg_executing()		return the name of the register being executed
    	reg_recording()		return the name of the register being recorded

    Text Properties:				*text-property-functions*
    	prop_add()		attach a property at a position
    	prop_add_list()		attach a property at multiple positions
    	prop_clear()		remove all properties from a line or lines
    	prop_find()		search for a property
    	prop_list()		return a list of all properties in a line
    	prop_remove()		remove a property from a line
    	prop_type_add()		add/define a property type
    	prop_type_change()	change properties of a type
    	prop_type_delete()	remove a text property type
    	prop_type_get()		return the properties of a type
    	prop_type_list()	return a list of all property types

    Sound:							*sound-functions*
    	sound_clear()		stop playing all sounds
    	sound_playevent()	play an event's sound
    	sound_playfile()	play a sound file
    	sound_stop()		stop playing a sound

    Various:					*various-functions*
    	mode()			get current editing mode
    	state()			get current busy state
    	visualmode()		last visual mode used
    	exists()		check if a variable, function, etc. exists
    	exists_compiled()	like exists() but check at compile time
    	has()			check if a feature is supported in Vim
    	changenr()		return number of most recent change
    	cscope_connection()	check if a cscope connection exists
    	did_filetype()		check if a FileType autocommand was used
    	diff()			diff two Lists of strings
    	eventhandler()		check if invoked by an event handler
    	getcellpixels()		get List of cell pixel size
    	getpid()		get process ID of Vim
    	getscriptinfo()		get list of sourced Vim scripts
    	getstacktrace()		get current stack trace of Vim scripts
    	getimstatus()		check if IME status is active
    	interrupt()		interrupt script execution
    	windowsversion()	get MS-Windows version
    	terminalprops()		properties of the terminal

    	libcall()		call a function in an external library
    	libcallnr()		idem, returning a number

    	undofile()		get the name of the undo file
    	undotree()		return the state of the undo tree for a buffer

    	shiftwidth()		effective value of 'shiftwidth'

    	wordcount()		get byte/word/char count of buffer

    	id()			get unique string for item to use as a key

    	luaeval()		evaluate |Lua| expression
    	mzeval()		evaluate |MzScheme| expression
    	perleval()		evaluate Perl expression
    	py3eval()		evaluate Python expression
    	pyeval()		evaluate Python expression
    	pyxeval()		evaluate |python_x| expression
    	rubyeval()		evaluate |Ruby| expression

    	debugbreak()		interrupt a program being debugged

    *41.7*	Defining a function

    Vim enables you to define your own functions.  The basic function declaration
    begins as follows:

    	def {name}({var1}, {var2}, ...): return-type
    	  {body}
    	enddef

    	Note:
    	Function names must begin with a capital letter.

    Let's define a short function to return the smaller of two numbers.  It starts
    with this line:

    	def Min(num1: number, num2: number): number

    This tells Vim that the function is named "Min", it takes two arguments that
    are numbers: "num1" and "num2" and returns a number.

    The first thing you need to do is to check to see which number is smaller:

    	if num1 < num2

    Let's assign the variable "smaller" the value of the smallest number:

    	var smaller: number
    	if num1 < num2
    	  smaller = num1
    	else
    	  smaller = num2
    	endif

    The variable "smaller" is a local variable.  It is declared to be a number,
    that way Vim can warn you for any mistakes.  Variables used inside a function
    are local unless prefixed by something like "g:", "w:", or "b:".

    	Note:
    	To access a global variable from inside a function you must prepend
    	"g:" to it.  Thus "g:today" inside a function is used for the global
    	variable "today", and "today" is another variable, local to the
    	function or the script.

    You now use the `return` statement to return the smallest number to the user.
    Finally, you end the function:

    	  return smaller
    	enddef

    The complete function definition is as follows:

    	def Min(num1: number, num2: number): number
    	  var smaller: number
    	  if num1 < num2
    	    smaller = num1
    	  else
    	    smaller = num2
    	  endif
    	  return smaller
    	enddef

    Obviously this is a verbose example.  You can make it shorter by using two
    return commands:

    	def Min(num1: number, num2: number): number
    	  if num1 < num2
    	    return num1
    	  endif
    	  return num2
    	enddef

    And if you remember the conditional expression, you need only one line:

    	def Min(num1: number, num2: number): number
    	  return num1 < num2 ? num1 : num2
    	enddef

    A user defined function is called in exactly the same way as a built-in
    function.  Only the name is different.  The Min function can be used like
    this:

    	echo Min(5, 8)

    Only now will the function be executed and the lines be parsed by Vim.
    If there are mistakes, like using an undefined variable or function, you will
    now get an error message.  When defining the function these errors are not
    detected.  To get the errors sooner you can tell Vim to compile all the
    functions in the script:

    	defcompile

    Compiling functions takes a little time, but does report errors early.  You
    could use `:defcompile` at the end of your script while working on it, and
    comment it out when everything is fine.

    For a function that does not return anything simply leave out the return type:

    	def SayIt(text: string)
    	  echo text
    	enddef

    If you want to return any kind of value, you can use the "any" return type:
    	def GetValue(): any
    This disables type checking for the return value, use only when needed.

    It is also possible to define a legacy function with `function` and
    `endfunction`.  These do not have types and are not compiled.  Therefore they
    execute much slower.

    USING A RANGE

    A line range can be used with a function call.  The function will be called
    once for every line in the range, with the cursor in that line.  Example:

    	def Number()
    	  echo "line " .. line(".") .. " contains: " .. getline(".")
    	enddef

    If you call this function with:

    	:10,15call Number()

    The function will be called six times, starting on line 10 and ending on line
    15.

    LISTING FUNCTIONS

    The `function` command lists the names and arguments of all user-defined
    functions:

    	:function
    	def <SNR>86_Show(start: string, ...items: list<string>)
    	function GetVimIndent()
    	function SetSyn(name)

    The "<SNR>" prefix means that a function is script-local.  |Vim9| functions
    will start with "def" and include argument and return types.  Legacy functions
    are listed with "function".

    To see what a function does, use its name as an argument for `function`:

    	:function SetSyn
    	1     if &syntax == ''
    	2       let &syntax = a:name
    	3     endif
    	   endfunction

    To see the "Show" function you need to include the script prefix, since
    multiple "Show" functions can be defined in different scripts.  To find
    the exact name you can use `function`, but the result may be a very long list.
    To only get the functions matching a pattern you can use the `filter` prefix:

    	:filter Show function
    	def <SNR>86_Show(start: string, ...items: list<string>)

    	:function <SNR>86_Show
    	1    echohl Title
    	2    echo "start is " .. start
    	etc.

    DEBUGGING

    The line number is useful for when you get an error message or when debugging.
    See |debug-scripts| about debugging mode.

    You can also set the 'verbose' option to 12 or higher to see all function
    calls.  Set it to 15 or higher to see every executed line.

    DELETING A FUNCTION

    To delete the SetSyn() function:

    	:delfunction SetSyn

    Deleting only works for global functions and functions in legacy script, not
    for functions defined in a |Vim9| script.

    You get an error when the function doesn't exist or cannot be deleted.

    FUNCTION REFERENCES

    Sometimes it can be useful to have a variable point to one function or
    another.  You can do it with a function reference variable.  Often shortened
    to "funcref".  Example:

    	def Right(): string
    	  return 'Right!'
    	enddef
    	def Wrong(): string
    	  return 'Wrong!'
    	enddef

    	var Afunc = g:result == 1 ? Right : Wrong
    	echo Afunc()
    	Wrong!

    This assumes "g:result" is not one.  See |Funcref| for details.

    Note that the name of a variable that holds a function reference must start
    with a capital.  Otherwise it could be confused with the name of a builtin
    function.

    FURTHER READING

    Using a variable number of arguments is introduced in section |50.2|.

    More information about defining your own functions here: |user-functions|.

    *41.8*	Lists and Dictionaries

    So far we have used the basic types String and Number.  Vim also supports
    three composite types: List, Tuple and Dictionary.

    A List is an ordered sequence of items.  The items can be any kind of value,
    thus you can make a List of numbers, a List of Lists and even a List of mixed
    items.  To create a List with three strings:

    	var alist = ['aap', 'noot', 'mies']

    The List items are enclosed in square brackets and separated by commas.  To
    create an empty List:

    	var alist = []

    You can add items to a List with the add() function:

    	var alist = []
    	add(alist, 'foo')
    	add(alist, 'bar')
    	echo alist
    	['foo', 'bar']

    List concatenation is done with +:

    	var alist = ['foo', 'bar']
    	alist = alist + ['and', 'more']
    	echo alist
    	['foo', 'bar', 'and', 'more']

    Or, if you want to extend a List with a function, use `extend()`:

    	var alist = ['one']
    	extend(alist, ['two', 'three'])
    	echo alist
    	['one', 'two', 'three']

    Notice that using `add()` will have a different effect than `extend()`:

    	var alist = ['one']
    	add(alist, ['two', 'three'])
    	echo alist
    	['one', ['two', 'three']]

    The second argument of add() is added as an item, now you have a nested list.

    FOR LOOP

    One of the nice things you can do with a List is iterate over it:

    	var alist = ['one', 'two', 'three']
    	for n in alist
    	  echo n
    	endfor
    	one
    	two
    	three

    This will loop over each element in List "alist", assigning each value to
    variable "n".  The generic form of a for loop is:

    	for {varname} in {list-expression}
    	  {commands}
    	endfor

    To loop a certain number of times you need a List of a specific length.  The
    range() function creates one for you:

    	for a in range(3)
    	  echo a
    	endfor
    	0
    	1
    	2

    Notice that the first item of the List that range() produces is zero, thus the
    last item is one less than the length of the list.  Detail: Internally range()
    does not actually create the list, so that a large range used in a for loop
    works efficiently.  When used elsewhere, the range is turned into an actual
    list, which takes more time for a long list.

    You can also specify the maximum value, the stride and even go backwards:

    	for a in range(8, 4, -2)
    	  echo a
    	endfor
    	8
    	6
    	4

    A more useful example, looping over all the lines in the buffer:

    	for line in getline(1, 50)
    	  if line =~ "Date: "
    	    echo line
    	  endif
    	endfor

    This looks into lines 1 to 50 (inclusive) and echoes any date found in there.

    For further reading see |Lists|.

    TUPLE

    A Tuple is an immutable ordered sequence of items.  An item can be of any
    type.  Items can be accessed by their index number.  To create a Tuple with
    three strings:

    	var atuple = ('one', 'two', 'three')

    The Tuple items are enclosed in parenthesis and separated by commas.  To
    create an empty Tuple:

    	var atuple = ()

    The |:for| loop can be used to iterate over the items in a Tuple similar to a
    List.

    For further reading see |Tuples|.

    DICTIONARIES

    A Dictionary stores key-value pairs.  You can quickly lookup a value if you
    know the key.  A Dictionary is created with curly braces:

    	var uk2nl = {one: 'een', two: 'twee', three: 'drie'}

    Now you can lookup words by putting the key in square brackets:

    	echo uk2nl['two']
    	twee

    If the key does not have special characters, you can use the dot notation:

    	echo uk2nl.two
    	twee

    The generic form for defining a Dictionary is:

    	{<key> : <value>, ...}

    An empty Dictionary is one without any keys:

    	{}

    The possibilities with Dictionaries are numerous.  There are various functions
    for them as well.  For example, you can obtain a list of the keys and loop
    over them:

    	for key in keys(uk2nl)
    	  echo key
    	endfor
    	three
    	one
    	two

    You will notice the keys are not ordered.  You can sort the list to get a
    specific order:

    	for key in sort(keys(uk2nl))
    	  echo key
    	endfor
    	one
    	three
    	two

    But you can never get back the order in which items are defined.  For that you
    need to use a List, it stores items in an ordered sequence.

    For further reading see |Dictionaries|.

    *41.9*	White space

    Blank lines are allowed in a script and ignored.

    Leading whitespace characters (blanks and TABs) are ignored, except when using
    |:let-heredoc| without "trim".

    Trailing whitespace is often ignored, but not always.  One command that
    includes it is `map`.  You have to watch out for that, it can cause hard to
    understand mistakes.  A generic solution is to never use trailing white space,
    unless you really need it.

    To include a whitespace character in the value of an option, it must be
    escaped by a "\" (backslash)  as in the following example:

    	:set tags=my\ nice\ file

    If it would be written as:

    	:set tags=my nice file

    This will issue an error, because it is interpreted as:

    	:set tags=my
    	:set nice
    	:set file

    |Vim9| script is very picky when it comes to white space.  This was done
    intentionally to make sure scripts are easy to read and to avoid mistakes.
    If you use white space sensibly it will just work.  When not you will get an
    error message telling you where white space is missing or should be removed.

    *41.10*	Line continuation

    In legacy Vim script line continuation is done by preceding a continuation
    line with a backslash:
    	let mylist = [
    			\ 'one',
    			\ 'two',
    			\ ]

    This requires the 'cpo' option to exclude the "C" flag.  Normally this is done
    by putting this at the start of the script:
    	let s:save_cpo = &cpo
    	set cpo&vim

    And restore the option at the end of the script:
    	let &cpo = s:save_cpo
    	unlet s:save_cpo

    A few more details can be found here: |line-continuation|.

    In |Vim9| script the backslash can still be used, but in most places it is not
    needed:
    	var mylist = [
    			'one',
    			'two',
    			]

    Also, the 'cpo' option does not need to be changed.  See
    |vim9-line-continuation| for details.

    *41.11*	Comments

    In |Vim9| script the character # starts a comment.  That character and
    everything after it until the end-of-line is considered a comment and
    is ignored, except for commands that don't consider comments, as shown in
    examples below.  A comment can start on any character position on the line,
    but not when it is part of the command, e.g. inside a string.

    The character " (the double quote mark) starts a comment in legacy script.
    This involves some cleverness to make sure double quoted strings are not
    recognized as comments (just one reason to prefer |Vim9| script).

    There is a little "catch" with comments for some commands.  Examples:

    	abbrev dev development	# shorthand
    	map <F3> o#include	# insert include
    	execute cmd		# do it
    	!ls *.c			# list C files

    - The abbreviation 'dev' will be expanded to 'development  # shorthand'.
    - The mapping of <F3> will actually be the whole line after the 'o# ....'
      including the '# insert include'.
    - The `execute` command will give an error.
    - The `!` command will send everything after it to the shell, most likely
      causing an error.

    There can be no comment after `map`, `abbreviate`, `execute` and `!` commands
    (there are a few more commands with this restriction).  For the `map`,
    `abbreviate` and `execute` commands there is a trick:

    	abbrev dev development|# shorthand
    	map <F3> o#include|# insert include
    	execute '!ls *.c'	|# do it

    With the '|' character the command is separated from the next one.  And that
    next command is only a comment.  The last command, using `execute` is a
    general solution, it works for all commands that do not accept a comment or a
    '|' to separate the next command.

    Notice that there is no white space before the '|' in the abbreviation and
    mapping.  For these commands, any character until the end-of-line or '|' is
    included.  As a consequence of this behavior, you don't always see that
    trailing whitespace is included:

    	map <F4> o#include

    Here it is intended, in other cases it might be accidental.  To spot these
    problems, you can highlight trailing spaces:
    	match Search /\s\+$/

    For Unix there is one special way to comment a line, that allows making a Vim
    script executable, and it also works in legacy script:
    	#!/usr/bin/env vim -S
    	echo "this is a Vim script"
    	quit

    *41.12*	Fileformat

    The end-of-line character depends on the system.  For Vim scripts it is
    recommended to always use the Unix fileformat.  Lines are then separated with
    the Newline character.  This also works on any other system.  That way you can
    copy your Vim scripts from MS-Windows to Unix and they still work.  See
    |:source_crnl|.  To be sure it is set right, do this before writing the file:

    	:setlocal fileformat=unix

    When using "dos" fileformat, lines are separated with CR-NL, two characters.
    The CR character causes various problems, better avoid this.

    Advance information about writing Vim script is in |usr_50|.

    Next chapter: |usr_42|  Add new menus

    Copyright: see |manual-copyright|  vim:tw=78:ts=8:noet:ft=help:norl:

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