ex: 51.rkt: implement `below`

3 files changed, 49 insertions, 1 deletions

diff --git a/ex/2/49.rkt b/ex/2/49.rkt
index 989f36d..b231318 100644
--- a/ex/2/49.rkt
+++ b/ex/2/49.rkt
@@ -5,7 +5,8 @@
 (provide
  frame-coord-map
  paint
- wave->painter)
+ wave->painter
+ x->painter)
 
 (require racket/draw)
 (require racket/snip)
diff --git a/ex/2/50.rkt b/ex/2/50.rkt
index a4f2433..3a67578 100644
--- a/ex/2/50.rkt
+++ b/ex/2/50.rkt
@@ -2,6 +2,8 @@
 
 #lang racket
 
+(provide transform-painter)
+
 (require "46.rkt")
 (require "47.rkt")
 (require "49.rkt")
diff --git a/ex/2/51.rkt b/ex/2/51.rkt
new file mode 100644
index 0000000..975c064
--- /dev/null
+++ b/ex/2/51.rkt
@@ -0,0 +1,45 @@
+;;;; License: CC0-1.0
+
+#lang racket
+
+(require "46.rkt")
+(require "49.rkt")
+(require "50.rkt")
+
+
+(define (beside painter1 painter2)
+  (let ((split-point (make-vect 0.5 0.0)))
+    (let ((paint-left
+           (transform-painter
+            painter1
+            (make-vect 0.0 0.0)
+            split-point
+            (make-vect 0.0 1.0)))
+          (paint-right
+           (transform-painter
+            painter2
+            split-point
+            (make-vect 1.0 0.0)
+            (make-vect 0.5 1.0))))
+      (lambda (frame)
+        (paint-left frame)
+        (paint-right frame)))))
+
+
+(define (below painter1 painter2)
+  (let ((split-point (make-vect 0.0 0.5)))
+    (let ((paint-above
+           (transform-painter
+            painter2
+            (make-vect 0.0 0.0)
+            (make-vect 1.0 0.0)
+            split-point))
+          (paint-below
+           (transform-painter
+            painter1
+            split-point
+            (make-vect 1.0 0.5)
+            (make-vect 0.0 1.0))))
+      (lambda (frame)
+        (paint-above frame)
+        (paint-below frame)))))