Object-oriented Software in Ada 95

116 Arrays
8.6.1 Multidimensional initializations
A cursor on a black and white screen can be defined by the following declaration of an object cursor_style:
Bits_Cursor : constant Positive := 5;
type Bit is new Integer range 0 .. 1;
type Cursor_Index is new Positive range 1 .. Bits_Cursor;
type Cursor is array( Cursor_Index,
Cursor_Index ) of Bit;
Cursor_Style : Cursor;
Black is represented by 1
White is represented by 0
Figure 8.3 Black and white cursor.
The cursor as illustrated in Figure 8.3 could be set up in cursor_style with any of the following three
declarations:
• by initializing every cell in the cursor individually:
Cursor_Style := Cursor'( (1, 0, 0, 0, 1),
(0, 1, 1, 1, 0),
(0, 0, 1, 0, 0),
(0, 1, 1, 1, 0),
(1, 0, 0, 0, 1) );
Note: The prefix to the array constant is optional in this case.
• by using an others clause to set up the white elements:
Cursor_Style := Cursor'( 1=> ( 1=>1, 5=>1, others => 0 ),
2=> ( 2..4 =>1, others => 0 ),
3=> ( 3=>1, others => 0 ),
4=> ( 2..4 =>1, others => 0 ),
5=> ( 1=>1, 5=>1, others => 0 ) );
• by using | clauses to combine any identical initializations:
Cursor_Style := Cursor'( 1|5=> ( 1|5 =>1, others => 0 ),
2|4=> ( 2..4=>1, others => 0 ),
3 => ( 3 =>1, others => 0 ) );
In a program using a colour monitor, the cursor could have been described as follows:
Bits_Cursor: constant Positive := 5;
type Colour is ( Red, Green, Blue );
type Intensity is range 0 .. 255;
type Pixel_Array is array( Colour ) of Intensity;
type Cursor_Index is new Positive range 1 .. Bits_Cursor;
type Cursor is array( Cursor_Index,
Cursor_Index ) of Pixel_Array;
Cursor_Style : Cursor;
© M A Smith - May not be reproduced without permission