messing around with classes: how to use arrays?

**eastmus** · 04-21-2009

this is my simple test class, showing 3 points: 1, 2, 3.
These are 3 separate fields.
I want to try to use arrays like p[3]={0,1,2}.
But i fail in getting that to work.

Maybe someone can help me?

Code:

#include <iostream>
#include <string>		// C++ string

using namespace std;

class point {
public:
	point();				// default constructor
	point( int initp1, int initp2, int initp3);		// constructor
	int getp1();			// accessor 
	int getp2();
	int getp3();
	void setpoint( int newp1, int newp2, int newp3 );	// mutator 
	void setp1( int newp1 );		// mutator p1
	void setp2( int newp2 );		// mutator p2
	void setp3( int newp3 );		// mutator p3
private:
	int p1;
	int p2;
	int p3;
};

point::point()					// default constructor
{	
	p1 = 0;
	p2 = 0;
	p3 = 0;
}

point::point( int initp1, int initp2, int initp3)		// constructor
{	
	p1 = initp1;
	p2 = initp2;
	p3 = initp3;
}

int point::getp1()				// accessor 
{	return p1;
}

int point::getp2()				// accessor
{	return p2;
}

int point::getp3()				// accessor 
{	return p3;
}

void point::setpoint( int newp1, int newp2, int newp3 )	// mutator 
{	
	p1 = newp1;
	p2 = newp2;
	p3 = newp3;
}

void point::setp1( int newp1 )			// mutator p1
{	p1 = newp1;
}

void point::setp2( int newp2 )			// mutator p2
{	p2 = newp2;
}

void point::setp3( int newp3 )			// mutator p3
{	p3 = newp3;
}

void main()
{	
	point p(1,2,3);

	cout << "points: " << p.getp1()  << " , " <<  p.getp2()  << " , " <<  p.getp3() << endl;

}

output:

Code:

points: 1 , 2 , 3

i have tried the following:

Code:

...
//keeping everything from above until main()
void main()
{	
	point p[3]={(1,2,3)};

	cout << "points: " << p[1].getp1   << endl;

}

or even rewriting the whole class with arrays in it but there are like 33 errors that are gibberish

Code:

#include <iostream>
#include <string>		// C++ string

using namespace std;

class point {
public:
	point();				// default constructor
	point( int initp1, int initp2, int initp3);		// constructor
	int getp[3]={};			// accessor 
	void setpoint( int newp1, int newp2, int newp3 );	// mutator 
	void setp[3]={int newp1, int newp2, int newp3};		// mutator 
private:
	int p[3];
};

point::point()					// default constructor
{	
	p[3] = {0,0,0};
}

point::point( int initp1, int initp2, int initp3)		// constructor
{	
	p[3] = {initp1, initp2, initp3};
}

int point::getp[0]()				// accessor 
{	return p[0];
}

int point::getp[1]()				// accessor
{	return p[1];
}

int point::getp[2]()				// accessor 
{	return p[2];
}

void point::setpoint( int newp1, int newp2, int newp3 )	// mutator 
{	
	p[3] = {newp1, newp2, newp3};
}

void point::setp[0]( int newp1 )			// mutator 
{	p[0] = newp1;
}

void point::setp[1]( int newp2 )			// mutator 
{	p[1] = newp2;
}

void point::setp[2]( int newp3 )			// mutator 
{	p[2] = newp3;
}

void main()
{	
	point p[3]={(1,2,3)};

	cout << "points: " << p[1].getp1   << endl;
}

could someone help me please ? i am struggling with this for quite a long time

thanks!

//edit

ok i found some code snippet through google and by understanding that code, i have adjusted my code to this:

Code:

#include <iostream>
#include <string>		// C++ string

using namespace std;

class point {
public:
	point();				// default constructor
	point( int initp1, int initp2, int initp3);		// constructor
	int getp1();			// accessor 
	int getp2();
	int getp3();
	void setpoint( int newp1, int newp2, int newp3 );	// mutator 
	void setp1( int newp1 );		// mutator p1
	void setp2( int newp2 );		// mutator p2
	void setp3( int newp3 );		// mutator p3
private:
	int p1;
	int p2;
	int p3;
};

point::point()					// default constructor
{	
	p1 = 0;
	p2 = 0;
	p3 = 0;
}

point::point( int initp1, int initp2, int initp3)		// constructor
{	
	p1 = initp1;
	p2 = initp2;
	p3 = initp3;
}

int point::getp1()				// accessor 
{	return p1;
}

int point::getp2()				// accessor
{	return p2;
}

int point::getp3()				// accessor 
{	return p3;
}

void point::setpoint( int newp1, int newp2, int newp3 )	// mutator 
{	
	p1 = newp1;
	p2 = newp2;
	p3 = newp3;
}

void point::setp1( int newp1 )			// mutator p1
{	p1 = newp1;
}

void point::setp2( int newp2 )			// mutator p2
{	p2 = newp2;
}

void point::setp3( int newp3 )			// mutator p3
{	p3 = newp3;
}

void main()
{	
	//point p[3]={1,2,3}; //error
	point p[3];

	cout << "points: " << p[1].getp1()   << endl;

}

but if i want to put values in the array p[3],
it still doesnt allow me.

**eastmus** · 04-21-2009

i found out i can use

Code:

void main()
{	
	point p[3];
	p[1].setp1(1);

	cout << "points: " << p[1].getp1()  << endl;

}

but its still not what i exactly want.
I'd like something like

Code:

void main()
{	
	point p[3];
	p[1]={1};

	cout << "points: " << p[1].getp1()  << endl;

}

but that doesnt work T_T
because i intend to add more values in that array

**whiteflags** · 04-21-2009

Creating an array involves the default constructor usually, so you would have to pick a mutator to change the elements.

C++ makes it a little easier with vector:

Code:

#include <vector>

// Declare point...

int main() {
   std::vector<point> parray;
   parray.push_back( point() );
   parray.push_back( point( 1, 0, -1 ) );
   parray.push_back( point( -2, 1, 2 ) );

   // Just to prove it works:
   for( std::vector<point>::size_type i = 0; i < parray.size(); i++ ) {
      std::cout << parray[i].getp1() << std::endl;
   }

}

Notice what happens with point's other constructor.

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