*vimeval.txt*	Nvim


		  VIM REFERENCE MANUAL	  by Bram Moolenaar


Expression evaluation	*vimscript* *expression* *expr* *E15* *eval* *eval.txt*

Using expressions is introduced in chapter 41 of the user manual |usr_41.txt|.

				      Type |gO| to see the table of contents.

==============================================================================
1. Variables						*variables*

1.1 Variable types ~
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There are seven types of variables:

							*Number* *Integer*
Number		A 32 or 64 bit signed number.  |expr-number|
		The number of bits is available in |v:numbersize|.
		Examples:  -123  0x10  0177  0o177  0b1011

Float		A floating point number. |floating-point-format| *Float*
		Examples: 123.456  1.15e-6  -1.1e3

String		A NUL terminated string of 8-bit unsigned characters (bytes).
		|expr-string| Examples: "ab\txx\"--"  'x-z''a,c'

Funcref		A reference to a function |Funcref|.
		Example: function("strlen")
		It can be bound to a dictionary and arguments, it then works
		like a Partial.
		Example: function("Callback", [arg], myDict)

List		An ordered sequence of items, see |List| for details.
		Example: [1, 2, ['a', 'b']]

Dictionary	An associative, unordered array: Each entry has a key and a
		value. |Dictionary|
		Examples: >
			{"blue": "#0000ff", "red": "#ff0000"}
			#{blue: "#0000ff", red: "#ff0000"}

Blob		Binary Large Object. Stores any sequence of bytes.  See |Blob|
		for details.
		Example: 0zFF00ED015DAF
		0z is an empty Blob.

The Number and String types are converted automatically, depending on how they
are used.

Conversion from a Number to a String is by making the ASCII representation of
the Number.  Examples:
	Number 123	-->	String "123" ~
	Number 0	-->	String "0" ~
	Number -1	-->	String "-1" ~
							*octal*
Conversion from a String to a Number is done by converting the first digits to
a number.  Hexadecimal "0xf9", Octal "017" or "0o17", and Binary "0b10"
numbers are recognized.  If the String doesn't start with digits, the result
is zero. Examples:
	String "456"	-->	Number 456 ~
	String "6bar"	-->	Number 6 ~
	String "foo"	-->	Number 0 ~
	String "0xf1"	-->	Number 241 ~
	String "0100"	-->	Number 64 ~
	String "0o100"	-->	Number 64 ~
	String "0b101"	-->	Number 5 ~
	String "-8"	-->	Number -8 ~
	String "+8"	-->	Number 0 ~

To force conversion from String to Number, add zero to it: >
	:echo "0100" + 0
<	64 ~

To avoid a leading zero to cause octal conversion, or for using a different
base, use |str2nr()|.

						*TRUE* *FALSE* *Boolean*
For boolean operators Numbers are used.  Zero is FALSE, non-zero is TRUE.
You can also use |v:false| and |v:true|.
When TRUE is returned from a function it is the Number one, FALSE is the
number zero.

Note that in the command: >
	:if "foo"
	:" NOT executed
"foo" is converted to 0, which means FALSE.  If the string starts with a
non-zero number it means TRUE: >
	:if "8foo"
	:" executed
To test for a non-empty string, use empty(): >
	:if !empty("foo")

<						*falsy* *truthy*
An expression can be used as a condition, ignoring the type and only using
whether the value is "sort of true" or "sort of false".  Falsy is:
	the number zero
	empty string, blob, list or dictionary
Other values are truthy.  Examples:
	0	falsy
	1	truthy
	-1	truthy
	0.0	falsy
	0.1	truthy
	''	falsy
	'x'	truthy
	[]	falsy
	[0]	truthy
	{}	falsy
	#{x: 1} truthy
	0z	falsy
	0z00	truthy

							*non-zero-arg*
Function arguments often behave slightly different from |TRUE|: If the
argument is present and it evaluates to a non-zero Number, |v:true| or a
non-empty String, then the value is considered to be TRUE.
Note that " " and "0" are also non-empty strings, thus considered to be TRUE.
A List, Dictionary or Float is not a Number or String, thus evaluate to FALSE.

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|List|, |Dictionary|, |Funcref|, and |Blob| types are not automatically
converted.

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When mixing Number and Float the Number is