Basic Types & User Defined Types 1. Objectives ..................................................................................... 2 2. Built-in Types and Primitive Types........................................... 2 3. Data Aggregates and Type Constructors .................................. 3 4. Constructors ................................................................................. 3 5. User-defined Types and Abstract Data Types .......................... 7 A. Bellaachia Page: 1 1. Objectives How to structure your data? How to organization your data? How to use primitive types to build user-defined types? How types are implemented? 2. Built-in Types and Primitive Types What is a type? . Values . Operations A primitive type mimics hardware units. We call primitive types those types that are not built from other types. Example: . Character is a primitive type in C, but String is not. Boolean is not a primitive type in C while it is in Java. Examples: . Booleans . Integers . Reals . Characters Benefits: . Hides underlying representation A. Bellaachia Page: 2 . Can do type checking at compile time . Can resolve overloaded functions at compile time . Programmer can specify the accuracy required 3. Data Aggregates and Type Constructors Definition: . An aggregate data type, also called compound object, consists of one or more data type objects. Example: o Arrays: consists of one or more elements of a single data type placed in contiguous locations from first to last. Constructors: . It is the method used to create an aggregate data type. Examples: o Cartesian Products o Sequences o Etc. 4. Constructors Cartesian Product: . A constructor used to create records and structures . Definition: Cartesian product of n sets A1, A2, A3, …, An is a set whose elements are ordered n-tuples (a1, a2, a3, …, an), where each ak belongs to Ak for 1kn. Example: A. Bellaachia Page: 3 o Structure in C o Records in Pascal and Ada. o A C example: #include <stdio.h> typedef struct { char name[30]; int age; char ssn[10]; } person; main (){ person myName = {"Bell", 20, "222222222"}; printf("Person Info: \n"); printf("\t\t%s\n\t\t%d\n\t\t%s\n", myName.name,myName.age, myName.ssn); } Mapping . Definition: o A mapping is a function from a set of values (domain) to a set of values (range): F: integer -> real . Array Constructor: is a mapping from a set of integers (index) to a set of values (content of the array). A. Bellaachia Page: 4 . Example: o Int myArray[5] ={-2,0,-3,4,300}; MyArray: 0 -2 MyArray: 1 0 MyArray: 2 -3 MyArray: 3 4 MyArray: 4 300 . Another Example: enum Colors {red, white, black, green, blue}; The compiler assigns an integer number to each name in the enumerated type starting from zero. Union and Discriminated Union . Union is a constructor that allows objects to be specified by a disjunctive of fields, e.g., field1 or field2 or ... or fieldn. An instance object has only one field: Save space. It is up to the programmer to remember which address is valid . Example: o Variant records in Pascal o Union structures in C: union mixed { int i; A. Bellaachia Page: 5 float f; char c; }; union mixed m; m.i = 10; Powerset: . Powerset(T): This is a constructor that creates a variable whose value is a set of elements of type T. T is called the base type. Example: o set type in Pascal o Java APIs: Sets. Sequence: . Sequences constructor allows the creation of objects whose number of elements is not specified. Objects will have arbitrary size. Example: sequential files, Vector, List in Java. Recursion . Recursion is a constructor that allows the size of an object to grow dynamically (add or delete elements). Example: Create the structure of a Linked List in C” typedef strcut { A. Bellaachia Page: 6 DoulyLinkedList * previous; Char name[30]; DoulyLinkedList * next; } doublyLinkedList; doublyLinkedList *head; 5. User-defined Types and Abstract Data Types The ability to create new data types using primitive data types. Example: typedef struct { int numerator; int denominator; } fraction; Define variables of type fraction: fraction f1, f2; Abstract Data Type (ADT) . It is an extension to the record or structure construct: Plus routines . C++/Java: ADT is a class construct. Constructor: It allocates and initializes the fields of an ADT. Languages usually provides a default constructor and default initializations. A. Bellaachia Page: 7 . Deconstructor: o It releases the memory allocated for an instance. o C++: a deconstructor has the name of the class prefixed by ‘~’ o Java: provide a garbage collector to clean memory allocated by an object. Example: C++ class fraction{ public: fraction (int i, int j){ numerator = i; denominator = j; } fraction (){ numerator = 0; denominator = 0; } fraction mul (fraction f1, fraction f2){ fraction f(0,0); f.numerator = f1.numerator * f1.numerator; f.denominator = f1.denominator * f1.denominator; return (f); } print (){ cout << numerator/denominator; } private: int numerator; int denominator; } A. Bellaachia Page: 8 Generic ADT: . An ADT that takes data types as parameters. C++ : template. Example: (www.cpluplus.com) // Create a template function that returns the // greater one of two objects we could use: #include <iostream.h> template <class T> T GetMax (T a, T b) { T result; result = (a>b)? a : b; return (result); } int main () { int i=5, j=6, k; long l=10, m=5, n; k=GetMax<int>(i,j); n=GetMax<long>(l,m); cout << k << endl; cout << n << endl; return 0; } A. Bellaachia Page: 9 .