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## Drawing : TurtleDrawing

This class is included as part of the file TurtleDrawing.tz.
To use this class in a simulation, include the line "@use TurtleDrawing."

### Class description:

> The TurtleDrawing class is a subclass of Drawing which allows drawing via a series of "logo turtle"-like commands. Drawing is accomplished by giving commands to a turtle moving around in 3D space. All commands are interpreted from the turtle's perspective, taking into account its current position and orientation.

> Unlike other angles used by breve, this class refers to angles as degrees and not radians to more closely match the behavior of traditional Logo implementations.

### Class methods:

> Manipulating the Turtle Avatar

> - get-turtle
> - hide-turtle
> - show-turtle

> Moving the Turtle

> - back
> - forward
> - pen-down
> - pen-up
> - pop-state
> - push-state
> - set-color
> - turn-down
> - turn-left
> - turn-right
> - turn-up

`back by length (double)`

> Moves the turtle back by length.

`forward by length (double)`

> Moves the turtle forward by length.

`get-turtle`

> Returns the turtle agent object (an instance of Mobile).

`hide-turtle`

> Hides the agent representing the turtle's current position and location. The turtle can be shown again using the method show-turtle.

`pen-down`

> Puts the pen down so that lines are drawn as the turtle moves. This is done by setting transparency to 1.0.

`pen-up`

> Lifts the pen so that no lines are drawn as the turtle moves. This is done by setting transparency to 0.0.

`pop-state`

> "Pops" a state from the state stack and makes it current. This method reenables the most recently "pushed" state (done with push-state).

`push-state`

> "Pushes" the current direction, color and point onto a stack so that it can be retrieved later using pop-state.

`set-color to color (vector) with-transparency trans = 1.0 (double)`

> Sets the current pen color to color, with optional transparency value trans.

`show-turtle`

> Shows the agent representing the turtle's current position and location. The turtle is visible by default, but can be hidden using hide-turtle.

`turn-down by angle (double)`

> Rotates the Turtle left by angle degrees.

`turn-left by angle (double)`

> Rotates the Turtle left by angle degrees.

`turn-right by angle (double)`

> Rotates the Turtle right by angle degrees.

`turn-up by angle (double)`

> Rotates the Turtle right by angle degrees.

Documentation created Thu Jul 3 18:18:12 2008