Vector 1: A Simple Vector Class

This example illustrates a simple vector class. The class defines and constructor, overloads the indexing operator, and defines a stream output (insertor) operator.

The indexing operator returns a reference to a vecotr element so that it can be used on the left hand side of an assignment or as an argument to a function that requires a reference.

The insertor operator is defined as a friend function, because the left operator is a stream. (In defining the rational class, we overloaded the insertor operator outside of the class. By overloading the operator in the class, this implementation saves a function call for every use of this operator.)

//
// Vector.C 
//
// A. B. Maccabe  3/10/97
//
// A simple vector class -- illustrates overloading the index operator
//    with array bounds checking
//
//
// this example illustrates a function that returns a reference (and
//   not a value).
//


#include <assert.h>
#include <iostream.h>

class Vector {
public:
    // constructor
    Vector( int lower, int upper ) {
	lb = lower;
	ub = upper;
	data = new double[upper-lower+1];
    };

    double& operator[] ( int indx ) {
	assert( lb<=indx && indx<=ub );
	
	return data[indx-lb];
    };

    friend ostream& operator << ( ostream &os, Vector v ) {
	for( int i = v.lb ; i <= v.ub ; i++ ) {
	    os << i << ':' << v.data[i-v.lb] << ' ';
	}
	return os;
    }
    
private:
    int lb, ub;
    double *data;
};

int main() {

    Vector v( 10, 20 );

    for( int i = 10 ; i <= 20 ; i++ ) {
	v[i] = i;
    }

    cout << v << endl;
}