Diagrams.TwoD.Path.Turtle.Internal

Authors : Michael Sloan at gmail, Deepak Jois [e-mail]

A module consisting of core types and functions to represent and operate on a "turtle".

More info about turtle graphics: http://en.wikipedia.org/wiki/Turtle_graphics

Turtle data types and accessors

data TurtleState

Core turtle data type. A turtle needs to keep track of its current position, like its position, heading etc., and all the paths that it has traversed so far.

We need to record a new path, everytime an attribute like style, pen position etc changes, so that we can separately track styles for each portion of the eventual path that the turtle took.

Constructors

TurtleState

Fields

isPenDown :: Bool

State of the pen. False means that turtle movements will not draw anything

penPos :: P2

Current position. This is updated everytime the turtle moves

heading :: Angle

Orientation of the turtle in 2D space, given in degrees

currTrail :: Located (Trail' Line R2)

Path traversed by the turtle so far, without any style or pen attributes changing

currPenStyle :: PenStyle

Current style of the pen

paths :: [TurtlePath]

List of paths along with style information, traversed by the turtle previously

Instances

Show TurtleState

data TurtlePath

Turtle path type that captures a list of paths and the style attributes associated with them

Constructors

TurtlePath

Fields

penStyle :: PenStyle

Style

turtleTrail :: Located (Trail R2)

Path

Instances

Show TurtlePath

data PenStyle

Style attributes associated with the turtle pen

Constructors

PenStyle

Fields

penWidth :: Double

Width of pen. Default is 1.0

penColor :: Colour Double

Color of pen. Default is black

Instances

Show PenStyle

Motion commands

forward

Arguments

:: Double

Distance to move

-> TurtleState

Turtle to move

-> TurtleState

Resulting turtle

Move the turtle forward by x units

backward

Arguments

:: Double

Distance to move

-> TurtleState

Turtle to move

-> TurtleState

Resulting turtle

Move the turtle backward by x units

left

Arguments

:: Double

Degree of turn

-> TurtleState

Turtle to turn

-> TurtleState

Resulting turtle

Turn the turtle anti-clockwise (left)

right

Arguments

:: Double

Degree of turn

-> TurtleState

Turtle to turn

-> TurtleState

Resulting turtle

Turn the turtle clockwise (right)

Pen style commands

setPenColor

Arguments

:: Colour Double

Width of Pen

-> TurtleState

Turtle to change

-> TurtleState

Resulting Turtle

alias of setPenColour

setPenColour

Arguments

:: Colour Double

Width of Pen

-> TurtleState

Turtle to change

-> TurtleState

Resulting Turtle

Set a new pen color for turtle.

If pen is down, this adds the current trail to paths and starts a new empty trail.

setPenWidth

Arguments

:: Double

Width of Pen

-> TurtleState

Turtle to change

-> TurtleState

Resulting Turtle

Set a new pen width for turtle.

If pen is down, this adds the current trail to paths and starts a new empty trail.

State setters

startTurtle :: TurtleState

The initial state of turtle. The turtle is located at the origin, at an orientation of 0 degrees with its pen position down. The pen style is defaultPenStyle.

setHeading

Arguments

:: Double

Degree of orientation

-> TurtleState

Turtle to orient

-> TurtleState

Resulting turtle

Turn the turtle to the given orientation, in degrees

towards

Arguments

:: P2

Point to orient turtle towards

-> TurtleState

Turtle to orient

-> TurtleState

Resulting turtle

Sets the turtle orientation towards a given location.

setPenPos

Arguments

:: P2

Position to place true

-> TurtleState

Turtle to position

-> TurtleState

Resulting turtle

Set the turtle X/Y position.

If pen is down and the current trail is non-empty, this will also add the current trail to the paths field.

Drawing control

penUp

Arguments

:: TurtleState

Turtle to modify

-> TurtleState

Resulting turtle

Puts the turtle pen in “Up” mode. Turtle movements will not draw anything

Does nothing if the pen was already up. Otherwise, it creates a turtle with the current trail added to paths.

penDown

Arguments

:: TurtleState

Turtle to modify

-> TurtleState

Resulting turtle

Puts the turtle pen in “Down” mode. Turtle movements will cause drawing to happen

Does nothing if the pen was already down. Otherwise, starts a new trail starting at the current position.

penHop :: TurtleState -> TurtleState

closeCurrent :: TurtleState -> TurtleState

Debugging

traceTurtle :: TurtleState -> TurtleState

Prints out turtle representation and returns it. Use for debugging

Diagram related

getTurtleDiagram :: Renderable (Path R2) b => TurtleState -> Diagram b R2

Creates a diagram from a turtle

Applies the styles to each trails in paths separately and combines them into a single diagram

getTurtlePath :: TurtleState -> Path R2

Creates a path from a turtle, ignoring the styles.