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Logo Turtle Computation Expression
namespace CExprs
module LogoTurtle =
type Distance_Unit = STEPS
type Rotation_Unit = GRADATIONS
type Rotation_Direction = | LEFT | RIGHT
let STEP = STEPS
let GRADATION = GRADATIONS
type Color = | RED | GREEN | BLUE
type Action =
| Walk of int * Distance_Unit
| Turn of int * Rotation_Unit * Rotation_Direction
| LiftPenUp
| PutPenDown
| PickColor of Color
type Turtle = Action seq
type AS_word = AS
type TO_word = TO
type THE_word = THE
type PEN_word = PEN
type UP_word = UP
type DOWN_word = DOWN
type TIMES_word = TIMES
type WHAT_word = WHAT
type DOES_word = DOES
type TurtleBuilder (name:string) =
member x.Yield(()) = Seq.empty : Turtle
[<CustomOperation("WALK", MaintainsVariableSpace = true)>]
member x.Walk(source:Turtle, nb, unit:Distance_Unit) : Turtle=
Seq.append source [Walk(nb, unit)]
[<CustomOperation("==", MaintainsVariableSpace = true)>]
member x.Op(source:Turtle, nb, unit:Distance_Unit) : Turtle=
Seq.append source [Walk(nb, unit)]
[<CustomOperation("TURN", MaintainsVariableSpace = true)>]
member x.Turn(source:Turtle, nb, unit:Rotation_Unit, to_word:TO_word,
the_word:THE_word, direction:Rotation_Direction) : Turtle=
Seq.append source [Turn(nb, unit, direction)]
[<CustomOperation("LIFT", MaintainsVariableSpace = true)>]
member x.LiftPenUp(source:Turtle, the_word:THE_word, pen_word:PEN_word,
up_word:UP_word) : Turtle =
Seq.append source [LiftPenUp]
[<CustomOperation("PUT", MaintainsVariableSpace = true)>]
member x.PutPenDown(source:Turtle, the_word:THE_word, pen_word:PEN_word,
down_word:DOWN_word) : Turtle =
Seq.append source [PutPenDown]
[<CustomOperation("PICK", MaintainsVariableSpace = true)>]
member x.PickColor(source:Turtle, the_word:THE_word, color:Color, pen_word:PEN_word) : Turtle =
Seq.append source [PickColor color]
[<CustomOperation("DO", MaintainsVariableSpace = true)>]
member x.Do(source:Turtle, as_word:AS_word, turtle:Turtle) : Turtle =
Seq.append source turtle
[<CustomOperation("REPEAT", MaintainsVariableSpace = true)>]
member x.Repeat(source:Turtle, nb:int, times_word:TIMES_word, what_word:WHAT_word,
turtle:Turtle, does_word:DOES_word) : Turtle =
Seq.append source (List.replicate nb turtle |> Seq.collect id)
static member (+) (t1:TurtleBuilder,t2:TurtleBuilder) : Turtle =
Seq.append (t1.Yield()) (t2.Yield())
let turtle name = new TurtleBuilder(name)
let t1 = Seq.empty : Turtle
let t2 = Seq.empty : Turtle
let x n1 n2 = turtle n1 + turtle n2
let example =
turtle "smith"
{
``==`` 4 STEPS
LIFT THE PEN UP
WALK 4 STEPS
TURN 3 GRADATIONS TO THE RIGHT
PICK THE GREEN PEN
PUT THE PEN DOWN
WALK 4 STEPS
}
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