5 files changed, 140 insertions, 0 deletions
diff --git a/coding-exercises/2/50.rkt b/coding-exercises/2/50.rkt
new file mode 100644
index 0000000..373e22a
--- /dev/null
+++ b/coding-exercises/2/50.rkt
@@ -0,0 +1,33 @@
+#lang racket
+(require "../../shared/pict.rkt")
+(require "../../shared/lists.rkt")
+(require sicp-pict)
+
+(define (flip-horiz painter)
+  (transform-painter
+    painter
+    (make-vect 1 0)
+    (make-vect 0 0)
+    (make-vect 1 1)))
+
+(define (flip-vert painter)
+  (transform-painter
+   painter
+   (make-vect 0 1)
+   (make-vect 1 1)
+   (make-vect 0 0)))
+
+(define (<-rotate180 painter)
+  (flip-horiz (flip-vert painter)))
+(define (<-rotate270 painter)
+  (transform-painter
+   painter
+   (make-vect 0 1)
+   (make-vect 0 0)
+   (make-vect 1 1)))
+
+(paint einstein)
+(paint (flip-horiz einstein))
+(paint (flip-vert einstein))
+(paint (<-rotate180 einstein))
+(paint (<-rotate270 einstein))
diff --git a/coding-exercises/2/51.rkt b/coding-exercises/2/51.rkt
new file mode 100644
index 0000000..5dcdd70
--- /dev/null
+++ b/coding-exercises/2/51.rkt
@@ -0,0 +1,29 @@
+#lang racket
+(require "../../shared/pict.rkt")
+
+(define (below painter1 painter2)
+  (let ((split-point (make-vect 0 0.5)))
+    (let ((top-painter
+            (transform-painter
+              painter2
+              split-point
+              (make-vect 1 0.5)
+              (make-vect 0 1)))
+          (bot-painter
+            (transform-painter
+              painter1
+              (make-vect 0 0)
+              (make-vect 1 0)
+              split-point)))
+      (lambda (frame)
+        (top-painter frame)
+        (bot-painter frame)))))
+
+(define (below2 painter1 painter2)
+  (<-rotate180
+    (<-rotate270
+     (beside (<-rotate270 painter1)
+             (<-rotate270 painter2)))))
+
+(paint (below einstein einstein))
+(paint (below2 einstein einstein))
diff --git a/coding-exercises/2/52.rkt b/coding-exercises/2/52.rkt
new file mode 100644
index 0000000..29f4e6d
--- /dev/null
+++ b/coding-exercises/2/52.rkt
@@ -0,0 +1,65 @@
+#lang racket
+(require "../../shared/pict.rkt")
+
+(define (wave frame)
+  (let ((wave-points
+          (list
+            (make-vect 0.24 0)
+            (make-vect 0.37 0.5)
+            (make-vect 0.3 0.6)
+            (make-vect 0.15 0.5)
+            (make-vect 0 0.7)
+            (make-vect 0 0.85)
+            (make-vect 0.15 0.65)
+            (make-vect 0.35 0.7)
+            (make-vect 0.4 0.7)
+            (make-vect 0.3 0.85)
+            (make-vect 0.36 1)
+            (make-vect 0.57 1)
+            (make-vect 0.62 0.855)
+            (make-vect 0.55 0.7)
+            (make-vect 0.65 0.7)
+            (make-vect 1 0.35)
+            (make-vect 1 0.25)
+            (make-vect 0.55 0.52)
+            (make-vect 0.7 0)
+            (make-vect 0.55 0)
+            (make-vect 0.45 0.4)
+            (make-vect 0.34 0)))
+        (smile
+          (list
+            (make-vect 0.4 0.8)
+            (make-vect 0.45 0.75)
+            (make-vect 0.5 0.75)
+            (make-vect 0.53 0.78))))
+    ((segments->painter
+               (append
+                 (line-points->segments smile)
+                 (line-points->segments
+                   (close-line
+                     wave-points)))) frame)))
+(paint wave)
+
+(define (corner-split painter n)
+  (if (= n 0)
+    painter
+    (let ((up (up-split painter (- n 1)))
+          (right (right-split painter (- n 1))))
+      (let ((top-left up)
+            (bottom-right right)
+            (corner (corner-split painter (- n 1))))
+        (beside (below painter top-left)
+                (below bottom-right corner))))))
+(paint (corner-split einstein 4))
+
+(define (square-limit painter n)
+  (let ((s (lambda (f)
+             (lambda (painter) (f (corner-split (flip-horiz painter) n))))))
+    ((square-of-four
+      (s flip-horiz)
+      (s (lambda (x) x))
+      (s <-rotate180)
+      (s flip-vert))
+     painter)))
+
+(paint (square-limit einstein 2))
diff --git a/coding-exercises/2/53.rkt b/coding-exercises/2/53.rkt
new file mode 100644
index 0000000..791bcd6
--- /dev/null
+++ b/coding-exercises/2/53.rkt
@@ -0,0 +1,9 @@
+#lang racket
+
+(list 'a 'b 'c)
+(list (list 'george))
+(cdr '((x1 x2) (y1 y2)))
+(cadr '((x1 x2) (y1 y2)))
+(pair? (car '(a short list)))
+(memq 'red '((red shoes) (blue socks)))
+(memq 'red '(red shoes blue socks))
diff --git a/coding-exercises/2/54.rkt b/coding-exercises/2/54.rkt
new file mode 100644
index 0000000..c59a91a
--- /dev/null
+++ b/coding-exercises/2/54.rkt
@@ -0,0 +1,4 @@
+#lang racket
+
+(equal? '(this is a list) '(this is a list))
+(equal? '(this is a list) '(this (is a) list))