function [hit,s] = ccylz(R,x,u,inside)

% Calculates the distance to a cylinder of radius R concentric and aligned
% with the z-axis

% Inputs
%%%%%%%%
%  double
%     R :  Radius of the cylinder (scalar)
%     x :  coordinates of the particle (row vector)
%     u :  direction cosines of the particle (row vector)
%  logical
%     inside: == true   particle thinks it is inside
%           : == false  particle thinks it is outside
%      

% Outputs
%%%%%%%%%
%  logical
%     hit: == true   particle would hit  the surface
%        : == false  particle would miss the surface
%
%  double
%     s: distance to the surface (if hit)
%     
% Internal variables
%  double
%     A:  Quadratic coefficient A (communicated to quadric) (scalar)
%     B:  Quadratic coefficient B (communicated to quadric) (scalar)
%     C:  Quadratic coefficient C (communicated to quadric) (scalar)


% Compute the quadratic coefficients
A = u(1).^2 + u(2).^2; 
B = u(1).*x(1)+ u(2).*x(2);
C = x(1).^2 + x(2).^2 - R.^2;

% Call the quadratic solver 
[hit,s] = quadric(A,B,C,inside);

return