package genericity;

/**
 * @mathmodel c : Colors, where Colors is the color of the pencil
 * @mathmodel s : int, where s is the length of the pencil
 * @constraint s > 0
 */
public interface Pencil {

	/**
	 * @return human-readable representation of <c,s> as a string
	 */
	public String toString();
	
	/**
	 * @param newColor is a valid color
	 * @alters this.c
	 * @ensures this.c = newColor
	 */
	public void setColor(Colors newColor);
	
	/**
	 * @param remove amount by which pencil will be shortened
	 * @requires remove >= 0
	 * @alters this.s
	 * @ensures remove < #s ==> s + remove = #s
	 */
	public void sharpen(int remove);
}