LEVIATHAN v962456e · 962456eee1

Lexical

Array and range literals

Array literals in square brackets, inclusive ranges with .., and range spreading inside an array literal.

since 0.1.0-alpha.1linuxwindowswasm

Description

An array literal lists its elements in square brackets: [1, 2, 3]. The empty literal [] is an array with no elements. A literal has type Array<T>, and every element must have the element type.

a..b is a range literal. It is inclusive at both ends and has type Range. A Range has start and end fields, and it can be iterated in a for loop.

A range written inside an array literal is spread into the array: [1..3, 7] is [1, 2, 3, 7].

Array and range forms

Array<int> a = [1, 2, 3];
Array<int> empty = [];
Array<int> r = [1..5];
Array<int> mixed = [1..3, 7, 10..11];
console.writeln(a);
console.writeln(empty.length());
console.writeln(r);
console.writeln(mixed);
Range span = 1..10;
console.writeln(span.start);
console.writeln(span.end);
int total = 0;
for (int i in 1..4) {
    total += i;
}
console.writeln(total);
Run it ▶
[1, 2, 3]
0
[1, 2, 3, 4, 5]
[1, 2, 3, 7, 10, 11]
1
10
10

Rules

  • An array literal is [e1, e2, ...]. A trailing comma is a syntax error.
  • Elements must share the element type: Array<int> a = [1, "x"]; is a compile error.
  • [] takes its element type from the declaration it initializes. var e = []; has nothing to infer the type from.
  • A range element in an array literal is spread, and its bounds may be any int expression ([1..n]).
  • a..b includes both a and b. A range whose end is below its start has no elements, so for (int i in 5..3) never runs.
  • Array literals can be nested: [[1, 2], [3]] is an Array<Array<int>>.
  • When an array literal initializes a sized numeric array such as Array<byte>, every element, including those spread from a range, is converted to the element type.

Examples

Nested arrays, a range with a variable bound, and an empty range:

Nested arrays and variable bounds

Array<Array<int>> grid = [[1, 2], [3]];
console.writeln(grid);
int n = 3;
console.writeln([1..n]);
Array<string> names = ["a", 'b'];
console.writeln(names.length());
for (int i in 5..3) {
    console.writeln("never printed");
}
console.writeln("done");
Run it ▶
[[1, 2], [3]]
[1, 2, 3]
2
done

Notes

The Array and Range classes and their methods are documented under std.Array and std.Range.

See also

  • Array — An ordered sequence of values of one type, Array<T>, with value semantics.
  • Range — A run of consecutive integers written a..b, including both ends.
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Char literals