295 lines
9.0 KiB
Plaintext
295 lines
9.0 KiB
Plaintext
[[painless-operators-array]]
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=== Operators: Array
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[[array-initialization-operator]]
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==== Array Initialization
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Use the `array initialization operator '[] {}'` to allocate a single-dimensional
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<<array-type, array type>> instance to the heap with a set of pre-defined
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elements. Each value used to initialize an element in the array type instance is
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cast to the specified element type value upon insertion. The order of specified
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values is maintained.
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*Errors*
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* If a value is not castable to the specified type value.
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*Grammar*
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[source,ANTLR4]
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----
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array_initialization: 'new' TYPE '[' ']' '{' expression_list '}'
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| 'new' TYPE '[' ']' '{' '}';
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expression_list: expression (',' expression);
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----
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*Example:*
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* Array initialization with static values.
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+
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[source,Painless]
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----
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<1> int[] x = new int[] {1, 2, 3};
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----
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+
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<1> declare `int[] x`;
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allocate `1-d int array` instance with `length [3]`
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-> `1-d int array reference`;
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store `int 1` to `index [0]` of `1-d int array reference`;
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store `int 2` to `index [1]` of `1-d int array reference`;
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store `int 3` to `index [2]` of `1-d int array reference`;
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store `1-d int array reference` to `x`;
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+
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* Array initialization with non-static values.
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+
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[source,Painless]
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----
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<1> int i = 1;
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<2> long l = 2L;
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<3> float f = 3.0F;
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<4> double d = 4.0;
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<5> String s = "5";
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<6> def array = new def[] {i, l, f*d, s};
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----
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+
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<1> declare `int i`;
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store `int 1` to `i`
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<2> declare `long l`;
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store `long 2` to `l`
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<3> declare `float f`;
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store `float 3.0` to `f`
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<4> declare `double d`;
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store `double 4.0` to `d`
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<5> declare `String s`;
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store `String "5"` to `s`
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<6> declare `def array`;
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allocate `1-d def array` instance with `length [4]`
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-> `1-d def array reference`;
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load from `i` -> `int 1`;
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implicit cast `int 1` to `def` -> `def`;
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store `def` to `index [0]` of `1-d def array reference`;
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load from `l` -> `long 2`;
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implicit cast `long 2` to `def` -> `def`;
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store `def` to `index [1]` of `1-d def array reference`;
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load from `f` -> `float 3.0`;
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load from `d` -> `double 4.0`;
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promote `float 3.0` and `double 4.0`: result `double`;
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implicit cast `float 3.0` to `double 3.0` -> `double 3.0`;
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multiply `double 3.0` and `double 4.0` -> `double 12.0`;
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implicit cast `double 12.0` to `def` -> `def`;
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store `def` to `index [2]` of `1-d def array reference`;
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load from `s` -> `String "5"`;
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implicit cast `String "5"` to `def` -> `def`;
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store `def` to `index [3]` of `1-d def array reference`;
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implicit cast `1-d int array reference` to `def` -> `def`;
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store `def` to `array`
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[[array-access-operator]]
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==== Array Access
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Use the `array access operator '[]'` to store a value to or load a value from
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an <<array-type, array type>> value. Each element of an array type value is
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accessed with an `int` type value to specify the index to store/load. The range
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of elements within an array that are accessible is `[0, size)` where size is the
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number of elements specified at the time of allocation. Use a negative `int`
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type value as an index to access an element in reverse from the end of an array
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type value within a range of `[-size, -1]`.
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*Errors*
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* If a value other than an `int` type value or a value that is castable to an
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`int` type value is provided as an index.
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* If an element is accessed outside of the valid ranges.
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*Grammar*
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[source,ANTLR4]
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----
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brace_access: '[' expression ']'
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----
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*Examples*
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* Array access with a single-dimensional array.
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+
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[source,Painless]
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----
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<1> int[] x = new int[2];
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<2> x[0] = 2;
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<3> x[1] = 5;
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<4> int y = x[0] + x[1];
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<5> int z = 1;
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<6> int i = x[z];
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----
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+
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<1> declare `int[] x`;
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allocate `1-d int array` instance with `length [2]`
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-> `1-d int array reference`;
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store `1-d int array reference` to `x`
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<2> load from `x` -> `1-d int array reference`;
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store `int 2` to `index [0]` of `1-d int array reference`;
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<3> load from `x` -> `1-d int array reference`;
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store `int 5` to `index [1]` of `1-d int array reference`;
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<4> declare `int y`;
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load from `x` -> `1-d int array reference`;
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load from `index [0]` of `1-d int array reference` -> `int 2`;
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load from `x` -> `1-d int array reference`;
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load from `index [1]` of `1-d int array reference` -> `int 5`;
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add `int 2` and `int 5` -> `int 7`;
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store `int 7` to `y`
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<5> declare `int z`;
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store `int 1` to `z`;
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<6> declare `int i`;
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load from `x` -> `1-d int array reference`;
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load from `z` -> `int 1`;
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load from `index [1]` of `1-d int array reference` -> `int 5`;
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store `int 5` to `i`;
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+
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* Array access with the `def` type.
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+
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[source,Painless]
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----
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<1> def d = new int[2];
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<2> d[0] = 2;
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<3> d[1] = 5;
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<4> def x = d[0] + d[1];
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<5> def y = 1;
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<6> def z = d[y];
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----
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+
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<1> declare `def d`;
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allocate `1-d int array` instance with `length [2]`
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-> `1-d int array reference`;
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implicit cast `1-d int array reference` to `def` -> `def`;
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store `def` to `d`
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<2> load from `d` -> `def`
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implicit cast `def` to `1-d int array reference`
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-> `1-d int array reference`;
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store `int 2` to `index [0]` of `1-d int array reference`;
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<3> load from `d` -> `def`
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implicit cast `def` to `1-d int array reference`
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-> `1-d int array reference`;
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store `int 5` to `index [1]` of `1-d int array reference`;
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<4> declare `int x`;
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load from `d` -> `def`
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implicit cast `def` to `1-d int array reference`
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-> `1-d int array reference`;
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load from `index [0]` of `1-d int array reference` -> `int 2`;
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load from `d` -> `def`
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implicit cast `def` to `1-d int array reference`
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-> `1-d int array reference`;
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load from `index [1]` of `1-d int array reference` -> `int 5`;
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add `int 2` and `int 5` -> `int 7`;
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implicit cast `int 7` to `def` -> `def`;
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store `def` to `x`
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<5> declare `def y`;
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implicit cast `int 1` to `def` -> `def`;
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store `def ` to `y`;
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<6> declare `int i`;
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load from `d` -> `def`
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implicit cast `def` to `1-d int array reference`
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-> `1-d int array reference`;
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load from `y` -> `def`;
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implicit cast `def` to `int 1` -> `int 1`;
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load from `index [1]` of `1-d int array reference` -> `int 5`;
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implicit cast `int 5` to `def`;
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store `def` to `z`;
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+
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* Array access with a multi-dimensional array.
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+
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[source,Painless]
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----
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<1> int[][][] ia3 = new int[2][3][4];
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<2> ia3[1][2][3] = 99;
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<3> int i = ia3[1][2][3];
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----
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<1> declare `int[][][] ia`;
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allocate `3-d int array` instance with length `[2, 3, 4]`
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-> `3-d int array reference`;
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store `3-d int array reference` to `ia3`
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<2> load from `ia3` -> `3-d int array reference`;
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store `int 99` to `index [1, 2, 3]` of `3-d int array reference`
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<3> declare `int i`;
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load from `ia3` -> `3-d int array reference`;
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load from `index [1, 2, 3]` of `3-d int array reference` -> `int 99`;
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store `int 99` to `i`
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[[array-length-operator]]
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==== Array Length
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An array type value contains a read-only member field named `length`. The
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`length` field stores the size of the array as an `int` type value where size is
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the number of elements specified at the time of allocation. Use the
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<<field-access-operator, field access operator>> to load the field `length`
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from an array type value.
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*Examples*
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* Access the `length` field.
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[source,Painless]
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----
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<1> int[] x = new int[10];
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<2> int l = x.length;
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----
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<1> declare `int[] x`;
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allocate `1-d int array` instance with `length [2]`
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-> `1-d int array reference`;
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store `1-d int array reference` to `x`
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<2> declare `int l`;
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load `x` -> `1-d int array reference`;
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load `length` from `1-d int array reference` -> `int 10`;
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store `int 10` to `l`;
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[[new-array-operator]]
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==== New Array
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Use the `new array operator 'new []'` to allocate an array type instance to
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the heap. Specify the element type following the `new` token. Specify each
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dimension with the `[` and `]` tokens following the element type name. The size
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of each dimension is specified by an `int` type value in between each set of `[`
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and `]` tokens.
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*Errors*
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* If a value other than an `int` type value or a value that is castable to an
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`int` type value is specified for for a dimension's size.
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*Grammar*
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[source,ANTLR4]
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----
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new_array: 'new' TYPE ('[' expression ']')+;
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----
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*Examples*
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* Allocation of different array types.
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+
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[source,Painless]
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----
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<1> int[] x = new int[5];
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<2> x = new int[10];
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<3> int y = 2;
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<4> def z = new def[y][y*2];
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----
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+
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<1> declare `int[] x`;
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allocate `1-d int array` instance with `length [5]`
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-> `1-d int array reference`;
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store `1-d int array reference` to `x`
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<2> allocate `1-d int array` instance with `length [10]`
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-> `1-d int array reference`;
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store `1-d int array reference` to `x`
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<3> declare `int y`;
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store `int 2` to `y`;
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<4> declare `def z`;
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load from `y` -> `int 2 @0`;
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load from `y` -> `int 2 @1`;
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multiply `int 2 @1` by `int 2 @2` -> `int 4`;
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allocate `2-d int array` instance with length `[2, 4]`
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-> `2-d int array reference`;
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implicit cast `2-d int array reference` to `def` -> `def`;
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store `def` to `z`;
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