Object-oriented Software in Ada 95

Data structures 95
This initialization can be more elegantly expressed using a record aggregate which is then assigned to the
object mike.
Mike := (Name=> "Mike ", Height=> 183, Sex=> Male);
Note:
The construct:
(name => "Mike ", height => 183, sex => Male )
is a record aggregate.
The record aggregate can also be defined using the absolute position of the arguments or a mixture of absolute
and named arguments. For example, the following three assignments are all equal in effect.
Corinna := ( "Corinna ", 171, Female);
Corinna := (Name=> "Corinna ", Sex=> Female, Height=> 171);
Corinna := ( "Corinna ", Sex=> Female, Height=> 171);
Note:
A record aggregate must have all its components specified even if some components have default
values. Once a named parameter in an aggregate has been used, all parameters to the right must also
be named.
If there is only one member of the record aggregate then it must still be enclosed in brackets.
A data structure may be compared for equality or assigned. For example, using the declarations:
Corinna, Mike, Miranda : Person;
Taller : Person;
the following code can be written:
Mike := (Name=>"Mike ", Height=>183, Sex=>Male);
Corinna:= (Name=>"Corinna ", Height=>171, Sex=>Female);
Miranda:= (Name=>"Miranda ", Height=>74, Sex=>Female);
Taller := Mike;
if mike = Taller then
Put("Mike taller"); New_Line;
end if;
if Mike /= Taller and Corinna /= Taller then
Put("Miranda taller"); New_Line;
end if;
7.2.1 Other operations allowed on data structures
Chapter 12 describes how new meanings for the inbuilt operators in Ada can be defined. Using these techniques to
define an additional meaning for > between instances of a Person would allow the following to be written:
if Mike > Corinna then
Put("Mike taller"); New_Line;
else
Put("Corinna taller"); New_Line;
end if;
© M A Smith - May not be reproduced without permission