CS111 Turtle Contract

Turtles are cousins of buggles. Like buggles, they can move forward, backward, left, and right, and can leave trails with a pen in their bellies. Unlike buggles, they are not constrained to move in a grid. They also don't eat bagels.

Instances of the Turtle class represent whimsical creatures that inhabit an instance of the TurtleWorld class. Conceptually, every turtle has four abstract state variables:

position: A pair of x- and y-coordinates specifying the location of the turtle in turtleworld. These coordinates are double values, unlike buggle coordinates, which are int values.
heading: The angle the turtle is facing. This is a double value that expresses an angle between 0 and 360 degrees. 0 degrees points rightward along the x-axis.
color: The color of the turtle.
penDown?: A boolean (true/false) indicating whether the turtle's pen is down.

Constructor Methods

Turtle ()
Returns a new turtle at position (0.0,0.0) whose heading is 0, whose color is Color.red, and whose pen is down.

Instance Methods

public void fd(int n)
public void fd(double n)
Moves this turtle forward by length n in the direction of its current heading.

public void bd (int n)
public void bd (double n)
Moves this turtle backward by length n in the direction of its current heading.

public void lt (int angle)
public void lt (double angle)
Turns this turtle left by angle degrees.

public void rt (int angle)
public void lt (double angle)
Turns this turtle right by angle degrees.

public void pu ()
Raises this turtle's pen. When the pen is raised, the turtle leaves no trail when it moves.

public void pd ()
Lowers this turtle's pen. When the pen is lowered, the turtle leaves a trail when it moves.

public Point getPosition ()
Returns a point that indicates the current position of this turtle in turtleworld.

public void setPosition (Point p)
Changes the position of this turtle to be the point p.

public void setPosition (int x, int y)
public void setPosition (double x, double y)
Changes the position of this turtle to be (x,y).

public double getHeading ()
Returns the heading of this turtle.

public void setHeading (int d)
public void setHeading (double d)
Changes the heading of this turtle to be the angle d.

public Color getColor ()
Returns the color of this turtle.

public void setColor (Color c)
Changes the color of this turtle to be the color c.

public String toString ()
Returns a string representation of this turtle.