Category:LSL List

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A list is a special kind of data type which can contain zero or more elements.

Lists are signified by square brackets surrounding their elements; the elements inside are separated by commas.



(Note: to be clear for those who have other programming backgrounds, there are no arrays in LSL: only lists.)

Diverse Data Types

Not all elements in a list need to be the same type of element. In the same list, you can store strings, integers, floats, vectors, etc, right side by side.

Example: //a list with an integer, a float, a string, and a vector.

[1,14.154,"Isn't this fun?",<0,0,0>]

However, a list may not contain another list (i.e. you can't nest them.)

[1, "one", 2, "two"] + [3, "three"] returns [1, "one", 2, "two", 3, "three"]
not [1, "one", 2, "two", [3, "three"]]

When you add an element to a list, the list remembers automatically what data type the value was.

Generally, because you're the one adding something to a list, you know what datatype is in what place in the list, and you retrieve it out of the list with the appropriate llList2<type> function such as: llList2String, llList2Vector, etc. (more on this later.)

If for some reason, though, you need to test what data type an element is in a list, you can use the llGetListEntryType function.

Tip! When adding a float to a list, always add it with a decimal point (e.g 1.0 as opposed to 1) to ensure that it is preserved as a float.

Counting place in a list vs list length

It's important at the outset to note the following (which can trip up even experienced minds when they are battle-weary):


The length of this list is 3, because it has 3 elements in it.

BUT, counting to determine an element's place in its list (aka "indexing") starts at 0 -- NOT 1.

The position of "Yes" in the above list is 0, "No" is at position 1, and "Perhaps" is at position 2.

Consequently, if you have 7 elements in a list, the last item in the list will be at position 6.

List Limits

While a script is running, a list can grow dynamically as large as needed, limited only by the amount of memory that is available in the script.

However, at compile (aka save) time, there is a 72 element limit to pre-defined lists hardcoded in the script. Such long, predefined lists are common, for example, when someone is offering the user a plethora of colour choices.

Tip! If you really need 72 or more such choices in a pre-defined list, just make 2 (or more) lists that don't upset the compiler, and join them together in state_entry() or wherever appropriate:

biggerlist = biglist01 + biglist02;

Joining Lists (aka Concatenation)

Lists can be joined simply by using the + sign:

newlist = list01 + list02;

newlist = list01 + ["red","brown",<0,0,0>];

Extended List Operations

These functions have been created and contributed by LSL users to perform operations not covered by built-in LSL functions.

function purpose
ListItemDelete Removes one element from a list.
ListStridedUpdate Updates part of a strided list.
ListToWholeNumbers Given a list of floats, converts them all to whole numbers (aka integers.)
ListXorY Join two lists to make one new combined list, while also eliminating any resulting duplicates in the new list.
ListXandY This function examines two lists, and returns a new list composed of the elements that both lists have in common.
ListXnotY Show what x list has that y list is missing.
ListXxorY Returns a new list, composed of elements that were in either original script, but not both. Note: This is not the same as getting rid duplicates by preserving just one of each duplicated item. It goes further, and removes both items.
ListXequY Answers the question: is list X identical to list Y?
ListXneqY Answers the question: is list X different from list Y?
Replace Replaces a single occurrence of something in a list with something else that you specify.
Replace All Replaces all occurrences of 'from list' with those in 'to list' in 'src list'. Not as concise as the replace function above, but will handle multiple items at the same time.
ListUnique Given a list of elements, returns a list of only the unique individual elements in that list.