Arrays of Records

An array item may be of any type

• can have an array with each item being a record

Purpose:

• often want to represent a collection of information
• a simple database of information on something
  • each item has a number of attributes of interest => use a record
  • need this information for many items => use an array of records

Example

Result list for a sporting event:

• several items of information about each competitor
  • number, name, club, time to complete the event
  • => record
• several competitors
  • => array

    max_field : constant := 50;

    type Number is range 1 .. 1000;

    subtype String20 is String(1..20);

    type Time is digits 7 range 0.0 .. 600.0;

    type Competitor is record
        id_number : Number;
        name      : String20;
        club      : String20;
        run_time  : Time;
    end record;

   type Result_list is array (1 .. max_field) of Competitor;

   race1, race2 : Result_list;

Using Arrays of Records

Declarations

1. constants: subtype limits, array sizes
2. elementary types: subtypes, enumeration types, field types
3. record data type
4. array type: array of that record type
5. array variables

Referring to portions of the array:

• can refer to entire database (array of all records) for assignment, as an actual parameter, etc
  • eg   race2 := race1;
• can refer to one item (a record in the database)
  • eg race1 is an array of records, so race1(J) is a record
  • eg   Display_Competitor(race1(J));
• can refer to a field of one item in database

    race1(3).id_number := 23;

    get (race1(I).id_number);
 
    race1(J).name := "Joe Bloggs          ";

    PUT(race1(J).club);

    GET(race1(next).run_time);

Examples

Two example programs show the design and code of programs that involve arrays of records:

• rental details for a car rental company
• marks in CS1 for each student in each division at ADFA