>
: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
Notice that the last index is inclusive. If you prefer using an exclusive
index use the |slice()| method.
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]
To add items to a List in-place, you can use |:let+=| (|list-concatenation|): >
:let listA = [1, 2]
:let listA += [3, 4]
<
When two variables refer to the same List, changing one List in-place will
cause the referenced List to be changed in-place: >
:let listA = [1, 2]
:let listB = listA
:let listB += [3, 4]
:echo listA
[1, 2, 3, 4]
<
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,