class member functions.

Hi,

I have this code that displays graphical data:

Code:

Func::Func(Fct f, double r1, double r2, Point xy, 
		int cnt, double xscale, double yscale)
		:count(cnt), range1(r1), origin(xy)
		
{
	if(r2-range1<=0) error("bad graphing range");
	if(count <=0) error("non-positive graphing count");
	double dist = (r2-range1)/count;
	double r = range1;
	for(int i = 0; i<count; ++i) {
		add(Point(origin.x+int(r*xscale), origin.y-int(f(r)*yscale)));
		r+=dist;
	}
}

The Fct f, is a function that I pass in, such as square, factorial etc. It all works and the graphs are displayed using a simple graphics library used in the book.

A typical object is created as such:

Code:

Func s1(square,-10,11, Point(300,300), 400, 25, 25);

An exercise in the book asks me to create member functions to allow for parameter changes. For example, the Point(300, 300) above is the origin of the graph.

So I thought I would simple create a function as such:

Code:

void Func::set_origin(Point& p)
{
	origin = p;
	
}

And, then when I re-attach the graph to the window, the changes would be made. But this is not the case. Any body got any ideas?

Thanks.

A lot of your work is done in the constructor of Fct. After construction, just setting the origin isn't going to change your collection of points. I would move most of the logic from your constructor into a private method and call that method from your setter functions, or move the logic to a public method and make sure you call that method after calling your setter functions.

Originally Posted by pianorain

A lot of your work is done in the constructor of Fct. After construction, just setting the origin isn't going to change your collection of points. I would move most of the logic from your constructor into a private method and call that method from your setter functions, or move the logic to a public method and make sure you call that method after calling your setter functions.

Will give that a try tomorrow when i'm back on it.

So, in essence, you advise to just use the constructor to initialise the variables and thenuse functions to draw the graph? Then when I want to make amendments I can simply call the relevant member function?

Thanks.