Generics - Introduction

Generics - Introduction

Generics - Nutshell

• Generics provide the ability to create specialized versions of things
• Typically specialized for specific types

Generics - Context: Java

• Java has generic types
• ie generic classes and interfaces
• Example:

 
         ArrayList< Integer> a = new ArrayList< Integer>();
         

• LHS is a type: ArrayList of Integers, only
• RHS is a instance of ArrayList of Integers, only

Generics - Parameterized

• Class ArrayList is parameterized (ie has a parameter)
• Allows for creation of specialized versions
• A specialized version for the specified type

Generics in Ada

• Ada allows creation and use of generic
• Procedures
• Functions
• Packages


• Each can be parameterized with types, ...
• and values, and packages, and ...


• We will look first at using generic procedures and packages
• Then we will look at creating generic packages and (briefly) procedures


• Examples of use that we will look at:
• Generic procedure: Ada.Containers.Generic_Array_Sort
• Generic procedure: Ada.Containers.Generic_Constrained_Array_Sort
• Generic functions: Ada.Unchecked_Conversion - later
• Generic packages: Ada.Text_IO.Enumeration_IO - Enumeration Types

Generic Sorts

Generic Array Sort

• Simple example:

         type Array_Type is array(Natural range <>) of Integer;

         procedure sort is 
         

• Package Ada.Containers contains generic procedure Generic_Array_Sort
• To use this we must provide parameters:
• ItemType
• Index_Type
• Array_Type
• "<"

Generics - Parameterized

Generics - Parameterized

Generics - Parameterized

Generics - Parameterized

Generics - Benefits

• Write code once
• Benefits of strong typing

Generics - History

• Ada 83 - Generics too complicated!
• Java (1995) - by 2000: we need generics!
• Java 1.5 (2005): (renamed Java 5) added generics!