List
Lists are ordered collections of items of the same type, accessed by index.
Definition
Lists are defined with square brackets [], like so:
list: List/Text = [ 'apple', 'pizza', 'pear' ]
Lists do not allow mixing of types. The type of a list is determined by the first item added to it, consequently, empty lists are untyped.
Lists skip empty positions, so an item that evaluates to null is ignored:
a = 1
c = 3
[ a, b, c ] # outputs: [ 1, 3 ] (b is skipped over)
Access
Individual items
List items can be accessed individually with zero-based index call:
list(0) # 'apple'
list(2) # 'pear'
Negative values will index backwards, starting from -1 as the last item:
list(-1) # 'pear'
Accessing items that are out of valid indices will generate an error:
0 1 2 > 2
Error [ 'apple', 'pizza', 'pear' ] Error
< -3 -3 -2 -1
Selections
You can pass a second argument to perform an access call as a selection from "start" to "end" index, evaluating as inclusive indices.
Indexes for start and end work exactly the same as when accessing individual items, so negatives count from the last item and can be regressive. However, when using selections, no errors are generated when accessing out-of-bounds indices; instead, an empty list is returned.
list(0, 0) # [ 'apple' ]
list(4, 8) # []
list(1, -1) # [ 'pizza', 'pear' ]
The same works for range syntax (..):
list(0..0) # [ 'apple' ]
list(4..8) # []
list(1..-1) # [ 'pizza', 'pear' ]
Yet, with ranges, one index can be left blank, and it assumes start from the first or end on the last item:
list(..1) # [ 'apple', 'pizza' ]
list(1..) # [ 'pizza', 'pear' ]
Nested lists
A matrix can be used and accessed like so:
matrix = [
[ 1, 2, 3 ]
[ 4, 5, 6 ]
]
matrix(1)(0) # yields 4 (1: second line, then 0: first index)
for simplicity, the example uses a 2D matrix, but could be n-dimensional
Operations
==equal!=not equal+addition (concatenation effect)-subtraction (difference effect)&logical AND|logical OR
logical AND/OR evaluate empty lists as
false, otherwisetrue
List addition (concatenation)
The list addition operation allows you to combine two lists into a new list:
x = [1, 2, 2, 3]
y = [3, 3, 4, 4]
x + y # result: [1, 2, 2, 3, 3, 3, 4, 4]
In this case, using the addition operator + to merge lists x and y, the elements from both lists are combined into a single list. The order of the elements in the resulting list is determined by the order in which the lists were added.
there is no removal of duplicate elements during the concatenation
Quick-append
For better performance, you can take advantage of += operator, e.g.:
~ list += [ value ] # faster
# same effect as
~ list = []
list = list + [ value ] # concatenation (slower)
Another detail of the += operator, which also applies to other types, is the automatic initialization by omission, where if the entry has not yet been declared previously, it acts as a simple assignment.
List subtraction (difference)
The list subtraction operation allows you to remove elements from the second operand that are present in the first operand, resulting in a list containing only unique values:
x = [ 1, 2, 2, 3 ]
y = [ 3, 3, 4, 4 ]
x - y # result: [ 1, 2 ]
y - x # result: [ 4 ]
In this case, when we subtract the list y from the list x, the elements with the value 3 are removed because they are present in both lists. The result is the list [1, 2]. Similarly, when we subtract the list x from the list y, the only remaining element is the value 4.
only exactly identical values are removed during the subtraction