linsolve() in a while loop with ginput()

Hi,

I've just almost finished my homework. To summarize, we are to draw a line through two user-defined points via ginput(). The user then clicks another point and we are to show the point of projection onto a line and its reflected point across the line. The user can click as many points to be projected and reflected until he/she decides to terminate ginput() with the return key.

I decided to implement this with systems of equation then using the linsolve() function. It works perfectly in a single iteration. In a while-loop, the calculations and plots are still correct but upon hitting the return key, it will spit out an error 'Dimensions must agree' involving linsolve(). I want to be able to hit the return key and print out to the command line "Program Ended". This error prevents me from doing so. How can I avoid this?

Here is my while loop:

while 1

        [p,q]=ginput(1);
        plot(p,q,'bo');
        originalPoint = [p,q]';

        %Calculate Projection 
        A = [x(2)-x(1) y(2)-y(1)
            y(1)-y(2) x(2)-x(1)];

        B= -[-p*(x(2)-x(1))-q*(y(2)-y(1))
            -y(1)*(x(2)-x(1))+(x(1)*(y(2)-y(1)))];

        X=linsolve(A,B);

        plot(X(1),X(2),'bp');

        %Calculate Reflection Point
        reflectPoint = [2*X(1),2*X(2)]'-[originalPoint(1),originalPoint(2)]';
        plot(reflectPoint(1),reflectPoint(2),'bh');

        key = get(gcf, 'CurrentKey');
    if(key == 'return')
        fprintf('Program Terminated\n');
        break
    end

end

[KSSV]

When we execute the code it shows error, x, y are undefined.