bool a: [0,1) true; [1,1] false; (1,3) true;
bool b: [0,1) false; [1,1] true; (1,3) false;

// [0.0,0.0]TF; (0.0,1.0)TF; [1.0,1.0]FT; (1.0,3.0)TF; 
bool c: [0.0,0.0]true;  (0.0,1.0)true;  [1.0,1.0]false; (1.0,3.0)true;
bool d: [0.0,0.0]false; (0.0,1.0)false; [1.0,1.0]true;  (1.0,3.0)false;

