List expressions
Literal
Creates a new list of the given elements. The elements can be of any type.
[1,2,3,4]
A list value can embed other list values.
[[1,2], [3,4], [5,6]]
Get element
a[i]
Accesses an element of the list a
at index i
. The index starts at 1
.
If the index is out of the range of the list, it returns null
.
[1,2,3,4][1]
// 1
[1,2,3,4][2]
// 2
[1,2,3,4][4]
// 4
[1,2,3,4][5]
// null
[1,2,3,4][0]
// null
If the index is negative, it starts counting the elements from the end of the list. The last
element of the list is at index -1
.
[1,2,3,4][-1]
// 4
[1,2,3,4][-2]
// 3
[1,2,3,4][-5]
// null
The index of a list starts at 1
. In other languages, the index starts at 0
.
Filter
a[c]
Filters the list a
by the condition c
. The result of the expression is a list that contains all
elements where the condition c
evaluates to true
. The other elements are excluded.
While filtering, the current element is assigned to the variable item
.
[1,2,3,4][item > 2]
// [3,4]
[1,2,3,4][item > 10]
// []
[1,2,3,4][even(item)]
// [2,4]
Some
some a in b satisfies c
Iterates over the list b
and evaluate the condition c
for each element in the list. The current
element is assigned to the variable a
.
It returns true
if c
evaluates to true
for one or more elements of b
. Otherwise, it
returns false
.
some x in [1,2,3] satisfies x > 2
// true
some x in [1,2,3] satisfies x > 5
// false
some x in [1,2,3] satisfies even(x)
// true
some x in [1,2], y in [2,3] satisfies x < y
// true
Every
Iterates over the list b
and evaluate the condition c
for each element in the list. The current
element is assigned to the variable a
.
It returns true
if c
evaluates to true
for all elements of b
. Otherwise, it
returns false
.
every x in [1,2,3] satisfies x >= 1
// true
every x in [1,2,3] satisfies x >= 2
// false
every x in [1,2,3] satisfies even(x)
// false
every x in [1,2], y in [2,3] satisfies x < y
// false