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Material Type: Notes; Professor: Bellaachia; Class: Software Paradigms; Subject: Computer Science; University: George Washington University; Term: Unknown 1989;
Typology: Study notes
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How to structure your data?
How to organization your data?
How to use primitive types to build user-defined types?
How types are implemented?
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
Can do type checking at compile time
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).
Example:
o Int myArray[5] ={-2,0,-3,4,300};
MyArray: 0 -
MyArray: 1 0
MyArray: 2 -
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., field 1
or
field 2 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;
float f;
char c;
} doublyLinkedList;
doublyLinkedList *head;
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.
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;
}
Generic ADT:
