Records

Fundamentals - Class Pair

What's in a class:
- Define a class for (X, Y) pairs (ie class Pair)
- Declare a variable of class Pair
- Allocate and object of class Pair
Can we have fields only?

in Java?
in Ada?

Fundamentals - Record Type Pair

Variables of record type contain only fields

        type Pair is record 
            ... 
        end record;

        p: Pair;

What memory is allocated

Notice: not a reference type

Notice: fields only

Fundamentals - Accessing Fields

In java

client code to access and modify Pair fields
Assume public access modifiers

 
        sop(p.x);
        p.y = 3;

In ada

 
        sop(p.x);
        p.y = 3;

But, where is type Pair declared?

Nested in procedure
In separate package

Context: Classes and Objects

Java: Classes contain fields (ie instance and class variables)
An objects is allocated using a class as a type
Objects (usually) have fields
Objects are only accessible via references (ie pointers)
Example

   class Pair{
      int x, y;
      ...
   }
   ...
   Pair p = new Pair();

Records

To create and use a record, we must first create a new type
A record type defines an ordered set of fields
Each field has a name and a type
Like java objects and ada arrays, we have separate type declaration and object allocation
Fields are accessed with dot notation, similar to java
Example: tryrecords1.adb (and prettified)
Memory allocation: not reference type!
Like an array, all fields can assigned in one statement

More Working with Records

Return record from function
Equality test

Example: tryrecords2.adb (and prettified)