n init_slider(no, min_x, max_x, initial_lb, initial_ub, x_template, on_slide){
	var slider = document.getElementById("interval_" + String(no));
	slider_min_x[no] = min_x;
	slider_max_x[no] = max_x;
	slider_lb[no] = initial_lb;
	slider_ub[no] = initial_ub;
	slider_down[no] = false;
	slider_template[no] = x_template;
	slider_value[no] = min_x - 1.0; // anything below min is "none"
	draw_slider(no);

	slider.addEventListener('mouseleave', function(e){
		slider_down[no] = false;
	}, false);

	slider.addEventLis