Graphics.WorldTurtle.Commands

This module contains all commands used to create, move and manipulate a turtle.

Creating a turtle.

data Turtle

The Turtle that is drawn on the canvas! Create a new turtle using makeTurtle.

Instances

Eq Turtle

Defined in Graphics.WorldTurtle.Internal.Sequence

Methods

(==) :: Turtle -> Turtle -> Bool

(/=) :: Turtle -> Turtle -> Bool

Ord Turtle

Defined in Graphics.WorldTurtle.Internal.Sequence

Methods

compare :: Turtle -> Turtle -> Ordering

(<) :: Turtle -> Turtle -> Bool

(<=) :: Turtle -> Turtle -> Bool

(>) :: Turtle -> Turtle -> Bool

(>=) :: Turtle -> Turtle -> Bool

max :: Turtle -> Turtle -> Turtle

min :: Turtle -> Turtle -> Turtle

makeTurtle :: TurtleCommand Turtle

Creates a new Turtle and displays it on the canvas. This turtle can then be manipulated! For example, to create a turtle and then move the turtle forward:

   main:: IO ()
   main = runTurtle $ do
     t <- makeTurtle
     forward 90 t
  

The default turtle starts at position (0, 0) and is orientated north.

makeTurtle'

Arguments

:: Point

Initial position of the turtle.

-> Float

Initial heading of the turtle.

-> Color

Color of the turtle and the turtle's pen.

-> TurtleCommand Turtle

The generated turtle.

This variant of makeTurtle takes a starting position, a starting orientation, and a color to apply to the turtle and the turtle's pen.

     myCommand :: TurtleCommand ()
     myCommand = do
       t1 <- makeTurtle' (0, 0)  0 green
       t2 <- makeTurtle' (0, 0) 90 red
       forward 90 t1 <|> forward 90 t2
   

See makeTurtle.

Movement commands.

type Point = (Float, Float)

A point on the x-y plane.

forward

Arguments

:: Float

Distance to move the turtle.

-> Turtle

The turtle to move.

-> TurtleCommand ()

Move the turtle forward by the specified distance, in the direction the turtle is headed.

fd :: Float -> Turtle -> TurtleCommand ()

Shorthand for forward.

backward

Arguments

:: Float

Distance to move the turtle.

-> Turtle

The turtle to move.

-> TurtleCommand ()

Move the turtle backward by the specified distance, in the direction the turtle is headed.

bk :: Float -> Turtle -> TurtleCommand ()

Shorthand for backward.

left

Arguments

:: Float

Rotation amount to apply to turtle.

-> Turtle

The turtle to rotate.

-> TurtleCommand ()

Turn a turtle left by the given degrees amount.

lt :: Float -> Turtle -> TurtleCommand ()

Shorthand for left.

right

Arguments

:: Float

Rotation amount to apply to turtle.

-> Turtle

The turtle to rotate.

-> TurtleCommand ()

Turn a turtle right by the given degrees amount.

rt :: Float -> Turtle -> TurtleCommand ()

Shorthand for right.

circle

Arguments

:: Float

Radius of the circle.

-> Float

Angle to travel in degrees. For example: 360 for a full circle or 180 for a semicircle.

-> Turtle

Turtle to move in a circle.

-> TurtleCommand ()

Draw an arc with a given radius. The center is radius units left of the turtle if positive. Otherwise radius units right of the turtle if negative.

The arc is drawn in an anticlockwise direction if the radius is positive, otherwise, it is drawn in a clockwise direction.

goto

Arguments

:: Point

Position to warp to.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Warps the turtle to a new position. The turtle jumps to this new position with no animation. If the pen is down then a line is drawn.

This does not affect the turtle's heading.

setPosition :: Point -> Turtle -> TurtleCommand ()

Alias of goto.

home :: Turtle -> TurtleCommand ()

Warps the turtle to its starting position (0, 0) and resets the orientation to North (90 degrees). No line is drawn moving the turtle.

setHeading

Arguments

:: Float

Heading to apply.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's heading. See heading.

setSpeed

Arguments

:: Float

New speed.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's speed. See speed.

setRotationSpeed

Arguments

:: Float

New rotation speed.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's rotation speed. See rotationSpeed.

Styling commands.

stamp

Arguments

:: Turtle

The turtle with the shape to be copied.

-> TurtleCommand ()

Stamp a copy of the turtle shape onto the canvas at the current turtle position.

representation

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Picture

Gets the turtle's representation as a Picture.

Query turtle's state.

position

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Point

Returned current point.

Returns the turtle's current position. Default (starting) position is (0, 0).

heading

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Float

Returned heading as angle in degrees.

Returns the turtle's heading.

0 is along the positive x-axis, going anticlockwise. So:

• East is 0 degrees.
• North is 90 degrees.
• West is 180 degrees.
• South is 270 degrees.

The default heading is North (90 degrees).

speed

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Float

Speed of turtle.

Returns the turtle's current speed. Speed is is distance per second. A speed of 0 is equivalent to no animation being performed and instant movement. The default value is 200.

rotationSpeed

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Float

Rotation speed of turtle.

Returns the turtle's current rotation speed. Rotation speed is is the speed in seconds it takes to do a full revolution. A speed of 0 is equivalent to no animation being performed and instant rotation. The default value is 20.

penColor

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Color

Returned current pen color.

Returns the turtle's pen color. The color of the turtle's pen.The default color is black.

penDown

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Bool

True if pen is down, false if not.

Returns whether the turtle's pen is down. When the turtle's pen is down it will draw a line when it moves. The default value is True.

penSize

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Float

Size of turtle's pen.

Returns the turtle's pen size. Defaults to 2.

visible

Arguments

:: Turtle

Turtle to query.

-> TurtleCommand Bool

True if turtle is visible, False if not.

Returns whether the turtle is visible. The default value is True.

Set rendering state.

setPenColor

Arguments

:: Color

New pen color to apply

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Set the turtle's pen color. See penColor.

setPenDown

Arguments

:: Bool

New state for pen flag. True for down. False for up.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's pen to down or up. See penDown.

setPenSize

Arguments

:: Float

New size for turtle's pen.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's pen size. See penSize.

setRepresentation

Arguments

:: Picture

Picture to apply.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's representation to a Picture. See representation. For example, to set the turtle as a red circle:

   import Graphics.WorldTurtle
   import qualified Graphics.Gloss.Data.Picture as G

   myCommand :: TurtleCommand ()
   myCommand = do
     t <- makeTurtle
     setPenColor red t
     setRepresentation (G.color red $ G.circleSolid 10) t
     forward 90 t
  

setVisible

Arguments

:: Bool

New state for visible flag.

-> Turtle

Turtle to modify.

-> TurtleCommand ()

Sets the turtle's visibility. See visible.

Canvas commands.

clear :: TurtleCommand ()

Clears all drawings form the canvas. Does not alter any turtle's state.

sleep :: Float -> TurtleCommand ()

Sleep for a given amount of time in seconds. When sleeping no animation runs. A negative value will be clamped to 0.

Common constants

east :: Float

0 degrees.

north :: Float

90 degrees.

west :: Float

180 degrees.

south :: Float

270 degrees.