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Operators: Array

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Operators: Array

Array Initialization

Use the array initialization operator '[] {}' to allocate a single-dimensional array type instance to the heap with a set of pre-defined elements. Each value used to initialize an element in the array type instance is cast to the specified element type value upon insertion. The order of specified values is maintained.

Errors

If a value is not castable to the specified type value.

Grammar

array_initialization: 'new' TYPE '[' ']' '{' expression_list '}'
                    | 'new' TYPE '[' ']' '{' '}';
expression_list: expression (',' expression);

Example:

Array initialization with static values.

int[] x = new int[] {1, 2, 3};

declare int[] x; allocate 1-d int array instance with length [3] → 1-d int array reference; store int 1 to index [0] of 1-d int array reference; store int 2 to index [1] of 1-d int array reference; store int 3 to index [2] of 1-d int array reference; store 1-d int array reference to x;

Array initialization with non-static values.

int i = 1;      
long l = 2L;    
float f = 3.0F; 
double d = 4.0; 
String s = "5"; 
def array = new def[] {i, l, f*d, s};

	declare `int i`; store `int 1` to `i`
	declare `long l`; store `long 2` to `l`
	declare `float f`; store `float 3.0` to `f`
	declare `double d`; store `double 4.0` to `d`
	declare `String s`; store `String "5"` to `s`
	declare `def array`; allocate `1-d def array` instance with `length [4]` → `1-d def array reference`; load from `i` → `int 1`; implicit cast `int 1` to `def` → `def`; store `def` to `index [0]` of `1-d def array reference`; load from `l` → `long 2`; implicit cast `long 2` to `def` → `def`; store `def` to `index [1]` of `1-d def array reference`; load from `f` → `float 3.0`; load from `d` → `double 4.0`; promote `float 3.0` and `double 4.0`: result `double`; implicit cast `float 3.0` to `double 3.0` → `double 3.0`; multiply `double 3.0` and `double 4.0` → `double 12.0`; implicit cast `double 12.0` to `def` → `def`; store `def` to `index [2]` of `1-d def array reference`; load from `s` → `String "5"`; implicit cast `String "5"` to `def` → `def`; store `def` to `index [3]` of `1-d def array reference`; implicit cast `1-d int array reference` to `def` → `def`; store `def` to `array`

Array Access

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Use the array access operator '[]' to store a value to or load a value from an array type value. Each element of an array type value is accessed with an int type value to specify the index to store/load. The range of elements within an array that are accessible is [0, size) where size is the number of elements specified at the time of allocation. Use a negative int type value as an index to access an element in reverse from the end of an array type value within a range of [-size, -1].

Errors

If a value other than an int type value or a value that is castable to an int type value is provided as an index.
If an element is accessed outside of the valid ranges.

Grammar

brace_access: '[' expression ']'

Examples

Array access with a single-dimensional array.

int[] x = new int[2]; 
x[0] = 2;             
x[1] = 5;             
int y = x[0] + x[1];  
int z = 1;            
int i = x[z];

	declare `int[] x`; allocate `1-d int array` instance with `length [2]` → `1-d int array reference`; store `1-d int array reference` to `x`
	load from `x` → `1-d int array reference`; store `int 2` to `index [0]` of `1-d int array reference`;
	load from `x` → `1-d int array reference`; store `int 5` to `index [1]` of `1-d int array reference`;
	declare `int y`; load from `x` → `1-d int array reference`; load from `index [0]` of `1-d int array reference` → `int 2`; load from `x` → `1-d int array reference`; load from `index [1]` of `1-d int array reference` → `int 5`; add `int 2` and `int 5` → `int 7`; store `int 7` to `y`
	declare `int z`; store `int 1` to `z`;
	declare `int i`; load from `x` → `1-d int array reference`; load from `z` → `int 1`; load from `index [1]` of `1-d int array reference` → `int 5`; store `int 5` to `i`;

Array access with the def type.

def d = new int[2];  
d[0] = 2;            
d[1] = 5;            
def x = d[0] + d[1]; 
def y = 1;           
def z = d[y];

	declare `def d`; allocate `1-d int array` instance with `length [2]` → `1-d int array reference`; implicit cast `1-d int array reference` to `def` → `def`; store `def` to `d`
	load from `d` → `def` implicit cast `def` to `1-d int array reference` → `1-d int array reference`; store `int 2` to `index [0]` of `1-d int array reference`;
	load from `d` → `def` implicit cast `def` to `1-d int array reference` → `1-d int array reference`; store `int 5` to `index [1]` of `1-d int array reference`;
	declare `int x`; load from `d` → `def` implicit cast `def` to `1-d int array reference` → `1-d int array reference`; load from `index [0]` of `1-d int array reference` → `int 2`; load from `d` → `def` implicit cast `def` to `1-d int array reference` → `1-d int array reference`; load from `index [1]` of `1-d int array reference` → `int 5`; add `int 2` and `int 5` → `int 7`; implicit cast `int 7` to `def` → `def`; store `def` to `x`
	declare `def y`; implicit cast `int 1` to `def` → `def`; store `def` to `y`;
	declare `int i`; load from `d` → `def` implicit cast `def` to `1-d int array reference` → `1-d int array reference`; load from `y` → `def`; implicit cast `def` to `int 1` → `int 1`; load from `index [1]` of `1-d int array reference` → `int 5`; implicit cast `int 5` to `def`; store `def` to `z`;

Array access with a multi-dimensional array.

int[][][] ia3 = new int[2][3][4]; 
ia3[1][2][3] = 99;                
int i = ia3[1][2][3];

	declare `int[][][] ia`; allocate `3-d int array` instance with length `[2, 3, 4]` → `3-d int array reference`; store `3-d int array reference` to `ia3`
	load from `ia3` → `3-d int array reference`; store `int 99` to `index [1, 2, 3]` of `3-d int array reference`
	declare `int i`; load from `ia3` → `3-d int array reference`; load from `index [1, 2, 3]` of `3-d int array reference` → `int 99`; store `int 99` to `i`

Array Length

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An array type value contains a read-only member field named length. The length field stores the size of the array as an int type value where size is the number of elements specified at the time of allocation. Use the field access operator to load the field length from an array type value.

Examples

Access the length field.

int[] x = new int[10]; 
int l = x.length;

	declare `int[] x`; allocate `1-d int array` instance with `length [2]` → `1-d int array reference`; store `1-d int array reference` to `x`
	declare `int l`; load `x` → `1-d int array reference`; load `length` from `1-d int array reference` → `int 10`; store `int 10` to `l`;

New Array

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Use the new array operator 'new []' to allocate an array type instance to the heap. Specify the element type following the new token. Specify each dimension with the [ and ] tokens following the element type name. The size of each dimension is specified by an int type value in between each set of [ and ] tokens.

Errors

If a value other than an int type value or a value that is castable to an int type value is specified for a dimension’s size.

Grammar

new_array: 'new' TYPE ('[' expression ']')+;

Examples

Allocation of different array types.

int[] x = new int[5];    
x = new int[10];         
int y = 2;               
def z = new def[y][y*2];

	declare `int[] x`; allocate `1-d int array` instance with `length [5]` → `1-d int array reference`; store `1-d int array reference` to `x`
	allocate `1-d int array` instance with `length [10]` → `1-d int array reference`; store `1-d int array reference` to `x`
	declare `int y`; store `int 2` to `y`;
	declare `def z`; load from `y` → `int 2 @0`; load from `y` → `int 2 @1`; multiply `int 2 @1` by `int 2 @2` → `int 4`; allocate `2-d int array` instance with length `[2, 4]` → `2-d int array reference`; implicit cast `2-d int array reference` to `def` → `def`; store `def` to `z`;

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