Arrays and Models

An array type holds an ordered, zero-indexed sequence of values of a single element type. It is written by wrapping the element type in [ and ] square brackets:

[int]
[string]
[{ a: int, b: string }]
[[int]]

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The element type may be any type, including a struct type and another array type.

A value of an array type is a model: it is what a for element iterates. A property of an array type, and an array literal, both act as models. Native code can also supply a model implementation for an array property, which the same operations act on.

Literals

An array literal lists its elements between [ and ], separated by commas:

export component Example {
    in-out property<[int]> list-of-int: [1, 2, 3];
    in-out property<[{a: int, b: string}]> list-of-structs: [{ a: 1, b: "hello" }, { a: 2, b: "world" }];
}

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Each element must have the array’s element type. An empty literal [] is a model with no elements.

Operations

The following operations apply to a value of an array type.

array.length reads the number of elements as an int. It is read-only; it cannot be assigned.
array[index] reads the element at the zero-based index. The index is an int.
array[index] = value writes the element at index. The array must be writable in that context.
array.push(value) appends value as a new last element. value must have the element type.
array.remove(index) removes the element at index.
array.insert(index, value) inserts value before the element at index, shifting later elements up. value must have the element type.
array.index-of(value) returns the index of the first element equal to value as an int, or -1 if no element matches. value must have the element type.

length, push, remove, insert, and index-of are members of the array; index is written with the [ ] operator.

Out-of-bounds behavior

Access outside the current bounds does not raise an error; each operation defines its own result.

array[index] with index < 0 or index >= array.length returns the default value of the element type.
array[index] = value with index < 0 or index >= array.length does nothing.
array.remove(index) accepts 0 <= index < array.length. Any other index leaves the array unchanged.
array.insert(index, value) accepts 0 <= index <= array.length, so inserting at array.length appends. Any other index leaves the array unchanged.

export component Example {
    in-out property<[int]> list-of-int: [1, 2, 3];

    out property <int> len: list-of-int.length;   // 3
    out property <int> first: list-of-int[0];      // 1
    out property <int> past-end: list-of-int[5];   // 0, the default int

    init => {
        // Both do nothing; list-of-int still holds [1, 2, 3].
        list-of-int.remove(4);
        list-of-int.insert(4, 10);
    }
}

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