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eval.txt
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eval.txt
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*eval.txt* For Vim version 8.0. Last change: 2017 Aug 11
VIM REFERENCE MANUAL by Bram Moolenaar
Expression evaluation *expression* *expr* *E15* *eval*
Using expressions is introduced in chapter 41 of the user manual |usr_41.txt|.
Note: Expression evaluation can be disabled at compile time. If this has been
done, the features in this document are not available. See |+eval| and
|no-eval-feature|.
1. Variables |variables|
1.1 Variable types
1.2 Function references |Funcref|
1.3 Lists |Lists|
1.4 Dictionaries |Dictionaries|
1.5 More about variables |more-variables|
2. Expression syntax |expression-syntax|
3. Internal variable |internal-variables|
4. Builtin Functions |functions|
5. Defining functions |user-functions|
6. Curly braces names |curly-braces-names|
7. Commands |expression-commands|
8. Exception handling |exception-handling|
9. Examples |eval-examples|
10. No +eval feature |no-eval-feature|
11. The sandbox |eval-sandbox|
12. Textlock |textlock|
13. Testing |testing|
{Vi does not have any of these commands}
==============================================================================
1. Variables *variables*
1.1 Variable types ~
*E712*
There are nine types of variables:
Number A 32 or 64 bit signed number. |expr-number| *Number*
64-bit Numbers are available only when compiled with the
|+num64| feature.
Examples: -123 0x10 0177 0b1011
Float A floating point number. |floating-point-format| *Float*
{only when compiled with the |+float| feature}
Examples: 123.456 1.15e-6 -1.1e3
*E928*
String A NUL terminated string of 8-bit unsigned characters (bytes).
|expr-string| Examples: "ab\txx\"--" 'x-z''a,c'
List An ordered sequence of items |List|.
Example: [1, 2, ['a', 'b']]
Dictionary An associative, unordered array: Each entry has a key and a
value. |Dictionary|
Example: {'blue': "#0000ff", 'red': "#ff0000"}
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)
Special |v:false|, |v:true|, |v:none| and |v:null|. *Special*
Job Used for a job, see |job_start()|. *Job* *Jobs*
Channel Used for a channel, see |ch_open()|. *Channel* *Channels*
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", 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 "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*
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")
<
*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 cause the mode to be
cleared. A List, Dictionary or Float is not a Number or String, thus
evaluates to FALSE.
*E745* *E728* *E703* *E729* *E730* *E731* *E908* *E910* *E913*
List, Dictionary, Funcref, Job and Channel types are not automatically
converted.
*E805* *E806* *E808*
When mixing Number and Float the Number is converted to Float. Otherwise
there is no automatic conversion of Float. You can use str2float() for String
to Float, printf() for Float to String and float2nr() for Float to Number.
*E891* *E892* *E893* *E894* *E907* *E911* *E914*
When expecting a Float a Number can also be used, but nothing else.
*no-type-checking*
You will not get an error if you try to change the type of a variable.
1.2 Function references ~
*Funcref* *E695* *E718*
A Funcref variable is obtained with the |function()| function, the |funcref()|
function or created with the lambda expression |expr-lambda|. It can be used
in an expression in the place of a function name, before the parenthesis
around the arguments, to invoke the function it refers to. Example: >
:let Fn = function("MyFunc")
:echo Fn()
< *E704* *E705* *E707*
A Funcref variable must start with a capital, "s:", "w:", "t:" or "b:". You
can use "g:" but the following name must still start with a capital. You
cannot have both a Funcref variable and a function with the same name.
A special case is defining a function and directly assigning its Funcref to a
Dictionary entry. Example: >
:function dict.init() dict
: let self.val = 0
:endfunction
The key of the Dictionary can start with a lower case letter. The actual
function name is not used here. Also see |numbered-function|.
A Funcref can also be used with the |:call| command: >
:call Fn()
:call dict.init()
The name of the referenced function can be obtained with |string()|. >
:let func = string(Fn)
You can use |call()| to invoke a Funcref and use a list variable for the
arguments: >
:let r = call(Fn, mylist)
<
*Partial*
A Funcref optionally binds a Dictionary and/or arguments. This is also called
a Partial. This is created by passing the Dictionary and/or arguments to
function() or funcref(). When calling the function the Dictionary and/or
arguments will be passed to the function. Example: >
let Cb = function('Callback', ['foo'], myDict)
call Cb()
This will invoke the function as if using: >
call myDict.Callback('foo')
This is very useful when passing a function around, e.g. in the arguments of
|ch_open()|.
Note that binding a function to a Dictionary also happens when the function is
a member of the Dictionary: >
let myDict.myFunction = MyFunction
call myDict.myFunction()
Here MyFunction() will get myDict passed as "self". This happens when the
"myFunction" member is accessed. When making assigning "myFunction" to
otherDict and calling it, it will be bound to otherDict: >
let otherDict.myFunction = myDict.myFunction
call otherDict.myFunction()
Now "self" will be "otherDict". But when the dictionary was bound explicitly
this won't happen: >
let myDict.myFunction = function(MyFunction, myDict)
let otherDict.myFunction = myDict.myFunction
call otherDict.myFunction()
Here "self" will be "myDict", because it was bound explicitly.
1.3 Lists ~
*list* *List* *Lists* *E686*
A List is an ordered sequence of items. An item can be of any type. Items
can be accessed by their index number. Items can be added and removed at any
position in the sequence.
List creation ~
*E696* *E697*
A List is created with a comma separated list of items in square brackets.
Examples: >
:let mylist = [1, two, 3, "four"]
:let emptylist = []
An item can be any expression. Using a List for an item creates a
List of Lists: >
:let nestlist = [[11, 12], [21, 22], [31, 32]]
An extra comma after the last item is ignored.
List index ~
*list-index* *E684*
An item in the List can be accessed by putting the index in square brackets
after the List. Indexes are zero-based, thus the first item has index zero. >
:let item = mylist[0] " get the first item: 1
:let item = mylist[2] " get the third item: 3
When the resulting item is a list this can be repeated: >
:let item = nestlist[0][1] " get the first list, second item: 12
<
A negative index is counted from the end. Index -1 refers to the last item in
the List, -2 to the last but one item, etc. >
:let last = mylist[-1] " get the last item: "four"
To avoid an error for an invalid index use the |get()| function. When an item
is not available it returns zero or the default value you specify: >
:echo get(mylist, idx)
:echo get(mylist, idx, "NONE")
List concatenation ~
Two lists can be concatenated with the "+" operator: >
:let longlist = mylist + [5, 6]
:let mylist += [7, 8]
To prepend or append an item turn the item into a list by putting [] around
it. To change a list in-place see |list-modification| below.
Sublist ~
*sublist*
A part of the List can be obtained by specifying the first and last index,
separated by a colon in square brackets: >
:let shortlist = mylist[2:-1] " get List [3, "four"]
Omitting the first index is similar to zero. Omitting the last index is
similar to -1. >
:let endlist = mylist[2:] " from item 2 to the end: [3, "four"]
:let shortlist = mylist[2:2] " List with one item: [3]
:let otherlist = mylist[:] " make a copy of the List
If the first index is beyond the last item of the List or the second item is
before the first item, the result is an empty list. There is no error
message.
If the second index is equal to or greater than the length of the list the
length minus one is used: >
:let mylist = [0, 1, 2, 3]
:echo mylist[2:8] " result: [2, 3]
NOTE: mylist[s:e] means using the variable "s:e" as index. Watch out for
using a single letter variable before the ":". Insert a space when needed:
mylist[s : e].
List identity ~
*list-identity*
When variable "aa" is a list and you assign it to another variable "bb", both
variables refer to the same list. Thus changing the list "aa" will also
change "bb": >
:let aa = [1, 2, 3]
:let bb = aa
:call add(aa, 4)
:echo bb
< [1, 2, 3, 4]
Making a copy of a list is done with the |copy()| function. Using [:] also
works, as explained above. This creates a shallow copy of the list: Changing
a list item in the list will also change the item in the copied list: >
:let aa = [[1, 'a'], 2, 3]
:let bb = copy(aa)
:call add(aa, 4)
:let aa[0][1] = 'aaa'
:echo aa
< [[1, aaa], 2, 3, 4] >
:echo bb
< [[1, aaa], 2, 3]
To make a completely independent list use |deepcopy()|. This also makes a
copy of the values in the list, recursively. Up to a hundred levels deep.
The operator "is" can be used to check if two variables refer to the same
List. "isnot" does the opposite. In contrast "==" compares if two lists have
the same value. >
:let alist = [1, 2, 3]
:let blist = [1, 2, 3]
:echo alist is blist
< 0 >
:echo alist == blist
< 1
Note about comparing lists: Two lists are considered equal if they have the
same length and all items compare equal, as with using "==". There is one
exception: When comparing a number with a string they are considered
different. There is no automatic type conversion, as with using "==" on
variables. Example: >
echo 4 == "4"
< 1 >
echo [4] == ["4"]
< 0
Thus comparing Lists is more strict than comparing numbers and strings. You
can compare simple values this way too by putting them in a list: >
:let a = 5
:let b = "5"
:echo a == b
< 1 >
:echo [a] == [b]
< 0
List unpack ~
To unpack the items in a list to individual variables, put the variables in
square brackets, like list items: >
:let [var1, var2] = mylist
When the number of variables does not match the number of items in the list
this produces an error. To handle any extra items from the list append ";"
and a variable name: >
:let [var1, var2; rest] = mylist
This works like: >
:let var1 = mylist[0]
:let var2 = mylist[1]
:let rest = mylist[2:]
Except that there is no error if there are only two items. "rest" will be an
empty list then.
List modification ~
*list-modification*
To change a specific item of a list use |:let| this way: >
:let list[4] = "four"
:let listlist[0][3] = item
To change part of a list you can specify the first and last item to be
modified. The value must at least have the number of items in the range: >
:let list[3:5] = [3, 4, 5]
Adding and removing items from a list is done with functions. Here are a few
examples: >
:call insert(list, 'a') " prepend item 'a'
:call insert(list, 'a', 3) " insert item 'a' before list[3]
:call add(list, "new") " append String item
:call add(list, [1, 2]) " append a List as one new item
:call extend(list, [1, 2]) " extend the list with two more items
:let i = remove(list, 3) " remove item 3
:unlet list[3] " idem
:let l = remove(list, 3, -1) " remove items 3 to last item
:unlet list[3 : ] " idem
:call filter(list, 'v:val !~ "x"') " remove items with an 'x'
Changing the order of items in a list: >
:call sort(list) " sort a list alphabetically
:call reverse(list) " reverse the order of items
:call uniq(sort(list)) " sort and remove duplicates
For loop ~
The |:for| loop executes commands for each item in a list. A variable is set
to each item in the list in sequence. Example: >
:for item in mylist
: call Doit(item)
:endfor
This works like: >
:let index = 0
:while index < len(mylist)
: let item = mylist[index]
: :call Doit(item)
: let index = index + 1
:endwhile
If all you want to do is modify each item in the list then the |map()|
function will be a simpler method than a for loop.
Just like the |:let| command, |:for| also accepts a list of variables. This
requires the argument to be a list of lists. >
:for [lnum, col] in [[1, 3], [2, 8], [3, 0]]
: call Doit(lnum, col)
:endfor
This works like a |:let| command is done for each list item. Again, the types
must remain the same to avoid an error.
It is also possible to put remaining items in a List variable: >
:for [i, j; rest] in listlist
: call Doit(i, j)
: if !empty(rest)
: echo "remainder: " . string(rest)
: endif
:endfor
List functions ~
*E714*
Functions that are useful with a List: >
:let r = call(funcname, list) " call a function with an argument list
:if empty(list) " check if list is empty
:let l = len(list) " number of items in list
:let big = max(list) " maximum value in list
:let small = min(list) " minimum value in list
:let xs = count(list, 'x') " count nr of times 'x' appears in list
:let i = index(list, 'x') " index of first 'x' in list
:let lines = getline(1, 10) " get ten text lines from buffer
:call append('$', lines) " append text lines in buffer
:let list = split("a b c") " create list from items in a string
:let string = join(list, ', ') " create string from list items
:let s = string(list) " String representation of list
:call map(list, '">> " . v:val') " prepend ">> " to each item
Don't forget that a combination of features can make things simple. For
example, to add up all the numbers in a list: >
:exe 'let sum = ' . join(nrlist, '+')
1.4 Dictionaries ~
*dict* *Dictionaries* *Dictionary*
A Dictionary is an associative array: Each entry has a key and a value. The
entry can be located with the key. The entries are stored without a specific
ordering.
Dictionary creation ~
*E720* *E721* *E722* *E723*
A Dictionary is created with a comma separated list of entries in curly
braces. Each entry has a key and a value, separated by a colon. Each key can
only appear once. Examples: >
:let mydict = {1: 'one', 2: 'two', 3: 'three'}
:let emptydict = {}
< *E713* *E716* *E717*
A key is always a String. You can use a Number, it will be converted to a
String automatically. Thus the String '4' and the number 4 will find the same
entry. Note that the String '04' and the Number 04 are different, since the
Number will be converted to the String '4'. The empty string can be used as a
key.
A value can be any expression. Using a Dictionary for a value creates a
nested Dictionary: >
:let nestdict = {1: {11: 'a', 12: 'b'}, 2: {21: 'c'}}
An extra comma after the last entry is ignored.
Accessing entries ~
The normal way to access an entry is by putting the key in square brackets: >
:let val = mydict["one"]
:let mydict["four"] = 4
You can add new entries to an existing Dictionary this way, unlike Lists.
For keys that consist entirely of letters, digits and underscore the following
form can be used |expr-entry|: >
:let val = mydict.one
:let mydict.four = 4
Since an entry can be any type, also a List and a Dictionary, the indexing and
key lookup can be repeated: >
:echo dict.key[idx].key
Dictionary to List conversion ~
You may want to loop over the entries in a dictionary. For this you need to
turn the Dictionary into a List and pass it to |:for|.
Most often you want to loop over the keys, using the |keys()| function: >
:for key in keys(mydict)
: echo key . ': ' . mydict[key]
:endfor
The List of keys is unsorted. You may want to sort them first: >
:for key in sort(keys(mydict))
To loop over the values use the |values()| function: >
:for v in values(mydict)
: echo "value: " . v
:endfor
If you want both the key and the value use the |items()| function. It returns
a List in which each item is a List with two items, the key and the value: >
:for [key, value] in items(mydict)
: echo key . ': ' . value
:endfor
Dictionary identity ~
*dict-identity*
Just like Lists you need to use |copy()| and |deepcopy()| to make a copy of a
Dictionary. Otherwise, assignment results in referring to the same
Dictionary: >
:let onedict = {'a': 1, 'b': 2}
:let adict = onedict
:let adict['a'] = 11
:echo onedict['a']
11
Two Dictionaries compare equal if all the key-value pairs compare equal. For
more info see |list-identity|.
Dictionary modification ~
*dict-modification*
To change an already existing entry of a Dictionary, or to add a new entry,
use |:let| this way: >
:let dict[4] = "four"
:let dict['one'] = item
Removing an entry from a Dictionary is done with |remove()| or |:unlet|.
Three ways to remove the entry with key "aaa" from dict: >
:let i = remove(dict, 'aaa')
:unlet dict.aaa
:unlet dict['aaa']
Merging a Dictionary with another is done with |extend()|: >
:call extend(adict, bdict)
This extends adict with all entries from bdict. Duplicate keys cause entries
in adict to be overwritten. An optional third argument can change this.
Note that the order of entries in a Dictionary is irrelevant, thus don't
expect ":echo adict" to show the items from bdict after the older entries in
adict.
Weeding out entries from a Dictionary can be done with |filter()|: >
:call filter(dict, 'v:val =~ "x"')
This removes all entries from "dict" with a value not matching 'x'.
Dictionary function ~
*Dictionary-function* *self* *E725* *E862*
When a function is defined with the "dict" attribute it can be used in a
special way with a dictionary. Example: >
:function Mylen() dict
: return len(self.data)
:endfunction
:let mydict = {'data': [0, 1, 2, 3], 'len': function("Mylen")}
:echo mydict.len()
This is like a method in object oriented programming. The entry in the
Dictionary is a |Funcref|. The local variable "self" refers to the dictionary
the function was invoked from.
It is also possible to add a function without the "dict" attribute as a
Funcref to a Dictionary, but the "self" variable is not available then.
*numbered-function* *anonymous-function*
To avoid the extra name for the function it can be defined and directly
assigned to a Dictionary in this way: >
:let mydict = {'data': [0, 1, 2, 3]}
:function mydict.len()
: return len(self.data)
:endfunction
:echo mydict.len()
The function will then get a number and the value of dict.len is a |Funcref|
that references this function. The function can only be used through a
|Funcref|. It will automatically be deleted when there is no |Funcref|
remaining that refers to it.
It is not necessary to use the "dict" attribute for a numbered function.
If you get an error for a numbered function, you can find out what it is with
a trick. Assuming the function is 42, the command is: >
:function {42}
Functions for Dictionaries ~
*E715*
Functions that can be used with a Dictionary: >
:if has_key(dict, 'foo') " TRUE if dict has entry with key "foo"
:if empty(dict) " TRUE if dict is empty
:let l = len(dict) " number of items in dict
:let big = max(dict) " maximum value in dict
:let small = min(dict) " minimum value in dict
:let xs = count(dict, 'x') " count nr of times 'x' appears in dict
:let s = string(dict) " String representation of dict
:call map(dict, '">> " . v:val') " prepend ">> " to each item
1.5 More about variables ~
*more-variables*
If you need to know the type of a variable or expression, use the |type()|
function.
When the '!' flag is included in the 'viminfo' option, global variables that
start with an uppercase letter, and don't contain a lowercase letter, are
stored in the viminfo file |viminfo-file|.
When the 'sessionoptions' option contains "global", global variables that
start with an uppercase letter and contain at least one lowercase letter are
stored in the session file |session-file|.
variable name can be stored where ~
my_var_6 not
My_Var_6 session file
MY_VAR_6 viminfo file
It's possible to form a variable name with curly braces, see
|curly-braces-names|.
==============================================================================
2. Expression syntax *expression-syntax*
Expression syntax summary, from least to most significant:
|expr1| expr2
expr2 ? expr1 : expr1 if-then-else
|expr2| expr3
expr3 || expr3 .. logical OR
|expr3| expr4
expr4 && expr4 .. logical AND
|expr4| expr5
expr5 == expr5 equal
expr5 != expr5 not equal
expr5 > expr5 greater than
expr5 >= expr5 greater than or equal
expr5 < expr5 smaller than
expr5 <= expr5 smaller than or equal
expr5 =~ expr5 regexp matches
expr5 !~ expr5 regexp doesn't match
expr5 ==? expr5 equal, ignoring case
expr5 ==# expr5 equal, match case
etc. As above, append ? for ignoring case, # for
matching case
expr5 is expr5 same |List| instance
expr5 isnot expr5 different |List| instance
|expr5| expr6
expr6 + expr6 .. number addition or list concatenation
expr6 - expr6 .. number subtraction
expr6 . expr6 .. string concatenation
|expr6| expr7
expr7 * expr7 .. number multiplication
expr7 / expr7 .. number division
expr7 % expr7 .. number modulo
|expr7| expr8
! expr7 logical NOT
- expr7 unary minus
+ expr7 unary plus
|expr8| expr9
expr8[expr1] byte of a String or item of a |List|
expr8[expr1 : expr1] substring of a String or sublist of a |List|
expr8.name entry in a |Dictionary|
expr8(expr1, ...) function call with |Funcref| variable
|expr9| number number constant
"string" string constant, backslash is special
'string' string constant, ' is doubled
[expr1, ...] |List|
{expr1: expr1, ...} |Dictionary|
&option option value
(expr1) nested expression
variable internal variable
va{ria}ble internal variable with curly braces
$VAR environment variable
@r contents of register 'r'
function(expr1, ...) function call
func{ti}on(expr1, ...) function call with curly braces
{args -> expr1} lambda expression
".." indicates that the operations in this level can be concatenated.
Example: >
&nu || &list && &shell == "csh"
All expressions within one level are parsed from left to right.
expr1 *expr1* *E109*
-----
expr2 ? expr1 : expr1
The expression before the '?' is evaluated to a number. If it evaluates to
|TRUE|, the result is the value of the expression between the '?' and ':',
otherwise the result is the value of the expression after the ':'.
Example: >
:echo lnum == 1 ? "top" : lnum
Since the first expression is an "expr2", it cannot contain another ?:. The
other two expressions can, thus allow for recursive use of ?:.
Example: >
:echo lnum == 1 ? "top" : lnum == 1000 ? "last" : lnum
To keep this readable, using |line-continuation| is suggested: >
:echo lnum == 1
:\ ? "top"
:\ : lnum == 1000
:\ ? "last"
:\ : lnum
You should always put a space before the ':', otherwise it can be mistaken for
use in a variable such as "a:1".
expr2 and expr3 *expr2* *expr3*
---------------
expr3 || expr3 .. logical OR *expr-barbar*
expr4 && expr4 .. logical AND *expr-&&*
The "||" and "&&" operators take one argument on each side. The arguments
are (converted to) Numbers. The result is:
input output ~
n1 n2 n1 || n2 n1 && n2 ~
|FALSE| |FALSE| |FALSE| |FALSE|
|FALSE| |TRUE| |TRUE| |FALSE|
|TRUE| |FALSE| |TRUE| |FALSE|
|TRUE| |TRUE| |TRUE| |TRUE|
The operators can be concatenated, for example: >
&nu || &list && &shell == "csh"
Note that "&&" takes precedence over "||", so this has the meaning of: >
&nu || (&list && &shell == "csh")
Once the result is known, the expression "short-circuits", that is, further
arguments are not evaluated. This is like what happens in C. For example: >
let a = 1
echo a || b
This is valid even if there is no variable called "b" because "a" is |TRUE|,
so the result must be |TRUE|. Similarly below: >
echo exists("b") && b == "yes"
This is valid whether "b" has been defined or not. The second clause will
only be evaluated if "b" has been defined.
expr4 *expr4*
-----
expr5 {cmp} expr5
Compare two expr5 expressions, resulting in a 0 if it evaluates to false, or 1
if it evaluates to true.
*expr-==* *expr-!=* *expr->* *expr->=*
*expr-<* *expr-<=* *expr-=~* *expr-!~*
*expr-==#* *expr-!=#* *expr->#* *expr->=#*
*expr-<#* *expr-<=#* *expr-=~#* *expr-!~#*
*expr-==?* *expr-!=?* *expr->?* *expr->=?*
*expr-<?* *expr-<=?* *expr-=~?* *expr-!~?*
*expr-is* *expr-isnot* *expr-is#* *expr-isnot#*
*expr-is?* *expr-isnot?*
use 'ignorecase' match case ignore case ~
equal == ==# ==?
not equal != !=# !=?
greater than > ># >?
greater than or equal >= >=# >=?
smaller than < <# <?
smaller than or equal <= <=# <=?
regexp matches =~ =~# =~?
regexp doesn't match !~ !~# !~?
same instance is is# is?
different instance isnot isnot# isnot?
Examples:
"abc" ==# "Abc" evaluates to 0
"abc" ==? "Abc" evaluates to 1
"abc" == "Abc" evaluates to 1 if 'ignorecase' is set, 0 otherwise
*E691* *E692*
A |List| can only be compared with a |List| and only "equal", "not equal" and
"is" can be used. This compares the values of the list, recursively.
Ignoring case means case is ignored when comparing item values.
*E735* *E736*
A |Dictionary| can only be compared with a |Dictionary| and only "equal", "not
equal" and "is" can be used. This compares the key/values of the |Dictionary|
recursively. Ignoring case means case is ignored when comparing item values.
*E694*
A |Funcref| can only be compared with a |Funcref| and only "equal", "not
equal", "is" and "isnot" can be used. Case is never ignored. Whether
arguments or a Dictionary are bound (with a partial) matters. The
Dictionaries must also be equal (or the same, in case of "is") and the
arguments must be equal (or the same).
To compare Funcrefs to see if they refer to the same function, ignoring bound
Dictionary and arguments, use |get()| to get the function name: >
if get(Part1, 'name') == get(Part2, 'name')
" Part1 and Part2 refer to the same function
When using "is" or "isnot" with a |List| or a |Dictionary| this checks if the
expressions are referring to the same |List| or |Dictionary| instance. A copy
of a |List| is different from the original |List|. When using "is" without
a |List| or a |Dictionary| it is equivalent to using "equal", using "isnot"
equivalent to using "not equal". Except that a different type means the
values are different: >
echo 4 == '4'
1
echo 4 is '4'
0
echo 0 is []
0
"is#"/"isnot#" and "is?"/"isnot?" can be used to match and ignore case.
When comparing a String with a Number, the String is converted to a Number,
and the comparison is done on Numbers. This means that: >
echo 0 == 'x'
1
because 'x' converted to a Number is zero. However: >
echo [0] == ['x']
0
Inside a List or Dictionary this conversion is not used.
When comparing two Strings, this is done with strcmp() or stricmp(). This
results in the mathematical difference (comparing byte values), not
necessarily the alphabetical difference in the local language.
When using the operators with a trailing '#', or the short version and
'ignorecase' is off, the comparing is done with strcmp(): case matters.
When using the operators with a trailing '?', or the short version and
'ignorecase' is set, the comparing is done with stricmp(): case is ignored.
'smartcase' is not used.
The "=~" and "!~" operators match the lefthand argument with the righthand
argument, which is used as a pattern. See |pattern| for what a pattern is.
This matching is always done like 'magic' was set and 'cpoptions' is empty, no
matter what the actual value of 'magic' or 'cpoptions' is. This makes scripts
portable. To avoid backslashes in the regexp pattern to be doubled, use a
single-quote string, see |literal-string|.
Since a string is considered to be a single line, a multi-line pattern
(containing \n, backslash-n) will not match. However, a literal NL character
can be matched like an ordinary character. Examples:
"foo\nbar" =~ "\n" evaluates to 1
"foo\nbar" =~ "\\n" evaluates to 0
expr5 and expr6 *expr5* *expr6*
---------------
expr6 + expr6 .. Number addition or |List| concatenation *expr-+*
expr6 - expr6 .. Number subtraction *expr--*
expr6 . expr6 .. String concatenation *expr-.*
For |Lists| only "+" is possible and then both expr6 must be a list. The
result is a new list with the two lists Concatenated.
expr7 * expr7 .. Number multiplication *expr-star*
expr7 / expr7 .. Number division *expr-/*
expr7 % expr7 .. Number modulo *expr-%*
For all, except ".", Strings are converted to Numbers.
For bitwise operators see |and()|, |or()| and |xor()|.
Note the difference between "+" and ".":
"123" + "456" = 579
"123" . "456" = "123456"
Since '.' has the same precedence as '+' and '-', you need to read: >
1 . 90 + 90.0
As: >
(1 . 90) + 90.0
That works, since the String "190" is automatically converted to the Number
190, which can be added to the Float 90.0. However: >
1 . 90 * 90.0
Should be read as: >
1 . (90 * 90.0)
Since '.' has lower precedence than '*'. This does NOT work, since this
attempts to concatenate a Float and a String.
When dividing a Number by zero the result depends on the value:
0 / 0 = -0x80000000 (like NaN for Float)
>0 / 0 = 0x7fffffff (like positive infinity)
<0 / 0 = -0x7fffffff (like negative infinity)
(before Vim 7.2 it was always 0x7fffffff)
When 64-bit Number support is enabled:
0 / 0 = -0x8000000000000000 (like NaN for Float)
>0 / 0 = 0x7fffffffffffffff (like positive infinity)
<0 / 0 = -0x7fffffffffffffff (like negative infinity)
When the righthand side of '%' is zero, the result is 0.
None of these work for |Funcref|s.
. and % do not work for Float. *E804*
expr7 *expr7*
-----
! expr7 logical NOT *expr-!*
- expr7 unary minus *expr-unary--*
+ expr7 unary plus *expr-unary-+*
For '!' |TRUE| becomes |FALSE|, |FALSE| becomes |TRUE| (one).
For '-' the sign of the number is changed.
For '+' the number is unchanged.
A String will be converted to a Number first.
These three can be repeated and mixed. Examples:
!-1 == 0
!!8 == 1
--9 == 9
expr8 *expr8*
-----
expr8[expr1] item of String or |List| *expr-[]* *E111*
*E909* *subscript*
If expr8 is a Number or String this results in a String that contains the
expr1'th single byte from expr8. expr8 is used as a String, expr1 as a
Number. This doesn't recognize multi-byte encodings, see `byteidx()` for
an alternative, or use `split()` to turn the string into a list of characters.
Index zero gives the first byte. This is like it works in C. Careful:
text column numbers start with one! Example, to get the byte under the
cursor: >
:let c = getline(".")[col(".") - 1]
If the length of the String is less than the index, the result is an empty
String. A negative index always results in an empty string (reason: backward
compatibility). Use [-1:] to get the last byte.
If expr8 is a |List| then it results the item at index expr1. See |list-index|
for possible index values. If the index is out of range this results in an
error. Example: >
:let item = mylist[-1] " get last item
Generally, if a |List| index is equal to or higher than the length of the
|List|, or more negative than the length of the |List|, this results in an
error.
expr8[expr1a : expr1b] substring or sublist *expr-[:]*
If expr8 is a Number or String this results in the substring with the bytes
from expr1a to and including expr1b. expr8 is used as a String, expr1a and
expr1b are used as a Number. This doesn't recognize multi-byte encodings, see
|byteidx()| for computing the indexes.
If expr1a is omitted zero is used. If expr1b is omitted the length of the
string minus one is used.
A negative number can be used to measure from the end of the string. -1 is
the last character, -2 the last but one, etc.
If an index goes out of range for the string characters are omitted. If
expr1b is smaller than expr1a the result is an empty string.
Examples: >
:let c = name[-1:] " last byte of a string