added repeat function and refactored relevant examples

examples/dune

@@ -97,3 +97,8 @@
  (name complex)
  (modules complex)
  (libraries joy))
+
+(executable 
+ (name repeat)
+ (modules repeat)
+ (libraries joy))

examples/higher_transforms.ml

@@ -2,19 +2,13 @@ open Joy.Shape
 
 (* Higher order transformations can be composed with `comp`,
    which applies its function args right-to-left.
-   This allows us to create complex series transformations,
-   that can be applied iteratively *)
+   This allows us to create complex series of transformations,
+   that can be applied iteratively with the repeat function *)
 let transform = compose (translate 10 10) (scale 0.9)
-let rec range a b = if a > b then [] else a :: range (a + 1) b
 
 let () =
   init ();
   let initial = rectangle ~x:(-250) ~y:(-250) 100 100 in
-  let match_list l =
-    match l with
-    | [] -> [ transform initial ]
-    | last :: _ -> transform last :: l
-  in
-  let shapes = List.fold_right (fun _ acc -> match_list acc) (range 0 32) [] in
-  show shapes;
+  let shapes = repeat 32 transform initial in
+  render_shape shapes;
   close ()

examples/repeat.ml

@@ -0,0 +1,16 @@
+open Joy.Shape 
+
+(* 
+   demonstration of the repeat function 
+   takes n, an operation, and an initial shape, and applies the operation 
+   iteratively to the initial shape n times
+   
+   adapted from the original Joy python library's examples 
+*)
+
+let () =
+  init ();
+  let circle = circle ~x: (-100) ~y: 0 50 in 
+  let shapes = repeat 10 (translate 10 0) circle in 
+  render_shape shapes;
+  close ();

lib/shape.ml

@@ -136,6 +136,16 @@ let rec rotate degrees shape =
 
 let compose f g x = g (f x)
 
+let rec range a b = if a >= b then [] else a :: range (a + 1) b  
+let repeat n op shape = 
+  let match_list l = 
+    match l with
+    | [] -> [ op shape ]
+    | last :: _ -> op last :: l
+  in
+  let shapes = List.fold_right (fun _ acc -> match_list acc) (range 0 n) [] in 
+  complex shapes
+
 let render_axes () =
   set_color (rgb 192 192 192);
   let half_x = size_x () / 2 in

lib/shape.mli

@@ -12,6 +12,7 @@ val show : shape list -> unit
 val scale : float -> shape -> shape
 val rotate : int -> shape -> shape
 val compose : ('a -> 'b) -> ('b -> 'c) -> 'a -> 'c
+val repeat : int -> (shape -> shape) -> shape -> shape
 val draw_axes : bool -> unit
 val set_dimensions : int -> int -> unit
 val init : unit -> unit