oberonjs/doc/wiki/eberon-dynamic-arrays.md

Dynamic arrays are similar to static arrays but their length can be changed at runtime - new elements can be added or removed.

Syntax

Dynamic arrays are declared in the same way as static arrays - 'dynamic' dimension is marked with '*':

a1: ARRAY * OF INTEGER;
a2: ARRAY *, * OF BOOLEAN;
a3: ARRAY *, 10, * OF CHAR;

Semantics

Initial length of dynamic array is 0. To add a new element add method is used:

array.add(value);

Added value type should be compatible with the array elements type. To remove element from array remove method is used:

array.remove(index);

INTEGER index specifies element index to remove. Method clear is used to remove all elements from array:

array.clear();

Dynamic arrays also have [[indexOf|eberon-array-methods]] method (similar to static arrays).

• Dynamic array can be passed as open array to procedure.
• Procedure can have dynamic array as VAR parameter and change content of passed array. But dynamic array cannot be passed as non-VAR paramater - ordinary open array should be used.
• Procedure can have dynamic array as a result - in this case a copy of array is returned.

Example:

MODULE Test;
TYPE
    A = ARRAY * OF INTEGER;
VAR
    a1, a2: A;

PROCEDURE returnDynamicArray(VAR a: A): A;
    RETURN a
END returnDynamicArray;

BEGIN
    a1.add(3);
    a2 := returnDynamicArray(a1);
    ASSERT(LEN(a2) = 1);
    ASSERT(a2[0] = 3);

    a1[0] := 5;
    ASSERT(a2[0] = 3); (*array was copied, a1 and a2 do not share elements*)
END Test.

• Dynamic array can be assigned to another dynamic array - destination array content is replaced by the content of source array, lenght became the same as the length of source array.
• Dynamic array can be assigned to open or static array but not vice versa.
• Element types should be compatible for all array assignment operations.
• Dynamic array cannot be assigned to NIL.