xlight = cosf(angle_to_light);
            ylight = sinf(angle_to_light);
            xrotate = A*xlight;// - B*xrepel;// + C*xrandom;
            yrotate = A*ylight;// - B*yrepel;// + C*yrandom;

            angle_to_rotate = acosf( xrotate/( sqrtf(xrotate*xrotate + yrotate*yrotate) ) );
            //printf("xrotate = %f,yrotate = %f,rotate = %f\n",xrotate,yrotate,angle_to_rotate);
            if (angle_to_rotate>0) {
                set_motors(0,kilo_turn_right);
            }
            else if (angle_to_rotate<0) {
                printf("hello\n" );
                set_motors(kilo_turn_left,0);
            }

由于某种原因，我从没获得angle_to_rotate的负值。基本上我的代码从不打印“ hello”。 angle_to_light可以是+ ve或-ve弧度吗？ acosf如何在c ++中正常工作？请帮助