diff --git a/.gitignore b/.gitignore
index 0f9e98a..5c40082 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
 old_ch2
 # ---> Scheme
+*.py
+*.png
 *.ss~
 *.ss#*
 .#*.ss
diff --git a/ex-2_33-43.scm b/ex-2_33-43.scm
index a1d2d7c..8099de5 100644
--- a/ex-2_33-43.scm
+++ b/ex-2_33-43.scm
@@ -219,9 +219,73 @@
 
 (display (unique-sum-triples 6 10)) (newline)
 
-(display "\nex-2.42\n")
+(display "\nex-2.42 - eight queens\n")
+
+; Creates a new list with numbers [1..n] cons'd to the current lists
+(define (add-numbers n xs)
+  (flatmap
+    (lambda (x) (map (lambda (i) (cons i x)) (enumerate-interval 1 n)))
+    xs))
+
+; Checks if the first queen on the board is safe relative to the other queens
+(define (safe? board)
+  (define (valid-position row diag board)
+    (if (null? board)
+      #t
+      (let ((cur_row (car board)))
+        (if (or (= row cur_row)           ; same row
+                (= (+ row diag) cur_row)  ; upper right diagonal
+                (= (- row diag) cur_row)) ; lower left diagonal
+          #f
+          (valid-position row (+ diag 1) (cdr board))))))
+  (valid-position (car board) 1 (cdr board)))
+
+(define empty-board (list nil))
+
+(define (queens n)
+  (define (queens-cols k)
+    (if (= k 0)
+      empty-board
+      (filter safe? (add-numbers n (queens-cols (- k 1))))))
+  (queens-cols n))
+
+(display (length (queens 8))) (newline)
+
+; Till here was my own implementation for practice.
+; Here is the official solution:
+
+(define (adjoin-position new-row k rest-of-queens)
+  (cons new-row rest-of-queens))
+
+(define (queens board-size)
+  (define empty-board nil)
+  (define (queen-cols k)
+    (if (= k 0)
+        (list empty-board)
+        (filter
+         (lambda (positions) (safe? positions)) ; removed k because we don't need it
+         (flatmap
+          (lambda (rest-of-queens)
+            (map (lambda (new-row)
+                   (adjoin-position new-row k rest-of-queens))
+                 (enumerate-interval 1 board-size)))
+          (queen-cols (- k 1))))))
+  (queen-cols board-size))
+
+(display (length (queens 8))) (newline)
 
 
-(display "\nex-2.43\n")
 
+(display "\nex-2.43 - see comments\n")
+;(flatmap
+; (lambda (new-row)
+;   (map (lambda (rest-of-queens)
+;          (adjoin-position new-row k rest-of-queens))
+;        (queen-cols (- k 1))))
+; (enumerate-interval 1 board-size))
+
+; Louis' implementation computes the queens for the remaining columns
+; board-size times for each column. That means for two columns the program is
+; two times slower. For three, two times times three times, in other words, the
+; execution time is (board-size! * T).
 
diff --git a/ex-2_44-52.scm b/ex-2_44-52.scm
index f79f94c..ac67f76 100644
--- a/ex-2_44-52.scm
+++ b/ex-2_44-52.scm
@@ -1,21 +1,269 @@
-(load "util.scm")
+(display "\nex-2.44 - a picture language\n")
+
+; One solution for 2.51
+(define (below painter1 painter2)
+  (let ((paint-top
+         (transform-painter painter2
+                            (make-vect 0.0 0.5)
+                            (make-vect 1.0 0.5)
+                            (make-vect 0.0 1.0)))
+        (paint-bottom
+         (transform-painter painter1
+                            (make-vect 0.0 0.0)
+                            (make-vect 1.0 0.0)
+                            (make-vect 0.0 0.5))))
+    (lambda (frame)
+      (lambda (draw-line)
+        ((paint-top frame) draw-line)
+        ((paint-bottom frame) draw-line)))))
+
+(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)
+        (lambda (draw-line)
+          ((paint-left frame) draw-line)
+          ((paint-right frame) draw-line))))))
+
+
+
+(define (right-split painter n)
+  (if (= n 0)
+      painter
+      (let ((smaller (right-split painter (- n 1))))
+        (beside painter (below smaller smaller)))))
+
+(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 (beside up up))
+              (bottom-right (below right right))
+              (corner (corner-split painter (- n 1))))
+          (beside (below painter top-left)
+                  (below bottom-right corner))))))
+
+(define (up-split painter n)
+  (if (= n 0)
+      painter
+      (let ((smaller (up-split painter (- n 1))))
+        (below painter (beside smaller smaller)))))
 
-(display "\nex-2.44\n")
 
 (display "\nex-2.45\n")
 
+(define (split main-placer smaller-placer)
+  (define (rec painter n)
+    (if (= n 0)
+      painter
+      (let ((smaller (rec painter (- n 1))))
+        (main-placer painter (smaller-placer smaller smaller)))))
+  rec)
+
+(define right-split (split beside below))
+(define up-split (split below beside))
+
 (display "\nex-2.46\n")
 
+(define (frame-coord-map frame)
+  (lambda (v)
+    (add-vect
+     (origin-frame frame)
+     (add-vect (scale-vect (xcor-vect v)
+                           (edge1-frame frame))
+               (scale-vect (ycor-vect v)
+                           (edge2-frame frame))))))
+
+(define make-vect cons)
+(define xcor-vect car)
+(define ycor-vect cdr)
+
+(define (add-vect v w)
+  (make-vect (+ (xcor-vect v) (xcor-vect w))
+             (+ (ycor-vect v) (ycor-vect w))))
+
+(define (sub-vect v w)
+  (make-vect (- (xcor-vect v) (xcor-vect w))
+             (- (ycor-vect v) (ycor-vect w))))
+
+(define (scale-vect s v)
+  (make-vect (* s (xcor-vect v)) (* s (ycor-vect v))))
+
+(define (frame-coord-map frame)
+  (lambda (v)
+    (add-vect
+     (origin-frame frame)
+     (add-vect (scale-vect (xcor-vect v)
+                           (edge1-frame frame))
+               (scale-vect (ycor-vect v)
+                           (edge2-frame frame))))))
+
 (display "\nex-2.47\n")
 
+(define (make-frame origin edge1 edge2)
+  (list origin edge1 edge2))
+
+(define origin-frame car)
+(define edge1-frame cadr)
+(define edge2-frame caddr)
+
+(define (make-frame origin edge1 edge2)
+  (cons origin (cons edge1 edge2)))
+
+(define origin-frame car)
+(define edge1-frame cadr)
+(define edge2-frame cddr)
+
 (display "\nex-2.48\n")
 
+(define (segments->painter segment-list)
+  (lambda (frame)
+    (lambda (draw-line)
+      (for-each
+       (lambda (segment)
+         (draw-line
+          ((frame-coord-map frame) (start-segment segment))
+          ((frame-coord-map frame) (end-segment segment))))
+       segment-list))))
+
+(define make-segment list)
+(define start-segment car)
+(define end-segment cadr)
+
 (display "\nex-2.49\n")
 
+(define simple-frame (make-frame (make-vect 0  1080)
+                                 (make-vect 1920 0)
+                                 (make-vect 0  -1080)))
+
+(define (make-line x1 y1 x2 y2)
+  (make-segment (make-vect x1 y1) (make-vect x2 y2)))
+
+(define painter-outline
+  (segments->painter
+    (list (make-line 0 0 0 1)
+          (make-line 0 0 1 0)
+          (make-line 1 0 1 1)
+          (make-line 0 1 1 1))))
+
+(define painter-x
+  (segments->painter
+    (list (make-line 0 0 1 1)
+          (make-line 0 1 1 0))))
+
+(define painter-diamond
+  (segments->painter
+    (list (make-line 0.5 0 0 0.5)
+          (make-line 0.5 0 1 0.5)
+          (make-line 0 0.5 0.5 1)
+          (make-line 1 0.5 0.5 1))))
+
+; from here: http://wiki.drewhess.com/wiki/SICP_exercise_2.49
+(define painter-wave
+  (segments->painter
+    (list (make-line 0.4 0 0.5 0.33)
+          (make-line 0.5 0.33 0.6 0.0)
+          (make-line 0.25 0.0 0.33 0.5)
+          (make-line 0.33 0.5 0.3 0.6)
+          (make-line 0.3 0.6 0.1 0.4)
+          (make-line 0.1 0.4 0.0 0.6)
+          (make-line 0.0 0.6 0.0 0.8)
+          (make-line 0.0 0.8 0.1 0.6)
+          (make-line 0.1 0.6 0.33 0.65)
+          (make-line 0.33 0.65 0.4 0.65)
+          (make-line 0.4 0.65 0.35 0.8)
+          (make-line 0.35 0.8 0.4 1.0)
+          (make-line 0.4 1.0 0.6 1.0)
+          (make-line 0.75 0.0 0.6 0.45)
+          (make-line 0.6 0.45 1.0 0.15)
+          (make-line 1.0 0.15 1.0 0.35)
+          (make-line 1.0 0.35 0.8 0.65)
+          (make-line 0.8 0.65 0.6 0.65)
+          (make-line 0.6 0.65 0.65 0.8)
+          (make-line 0.65 0.8 0.6 1.0))))
+
+(load "picture_language/draw.scm")
+
+(draw-to-py (painter-diamond simple-frame) "wave")
+
 (display "\nex-2.50\n")
 
+(define (transform-painter painter origin corner1 corner2)
+  (lambda (frame)
+    (let ((m (frame-coord-map frame)))
+      (let ((new-origin (m origin)))
+        (painter
+         (make-frame new-origin
+                     (sub-vect (m corner1) new-origin)
+                     (sub-vect (m corner2) new-origin)))))))
+
+(define (flip-vert painter)
+  (transform-painter painter
+                     (make-vect 0.0 1.0)   ; new origin
+                     (make-vect 1.0 1.0)   ; new end of edge1
+                     (make-vect 0.0 0.0))) ; new end of edge2
+
+(draw-to-py ((flip-vert painter-wave) simple-frame) "wave-flipped")
+
+(define (shrink-to-upper-right painter)
+  (transform-painter painter
+                     (make-vect 0.5 0.5)
+                     (make-vect 1.0 0.5)
+                     (make-vect 0.5 1.0)))
+
+(draw-to-py ((shrink-to-upper-right painter-wave) simple-frame) "wave-shrinked")
+
+(define (rotate90 painter)
+  (transform-painter painter
+                     (make-vect 1.0 0.0)
+                     (make-vect 1.0 1.0)
+                     (make-vect 0.0 0.0)))
+
+(draw-to-py ((rotate90 painter-wave) simple-frame) "wave-rotated")
+
+(define (flip-horiz painter)
+  (transform-painter painter
+                     (make-vect 1.0 0.0)   ; new origin
+                     (make-vect 0.0 0.0)   ; new end of edge1
+                     (make-vect 1.0 1.0))) ; new end of edge2
+
+(define (rotate180 painter)
+  (transform-painter painter
+                     (make-vect 1.0 1.0)
+                     (make-vect 0.0 1.0)
+                     (make-vect 1.0 0.0)))
+
+; both works of course
+(define (rotate270 painter)
+  (rotate90 (rotate90 (rotate90 painter))))
+
+(define (rotate270 painter)
+  (transform-painter painter
+                     (make-vect 0.0 1.0)
+                     (make-vect 0.0 0.0)
+                     (make-vect 1.0 1.0)))
+
+(draw-to-py ((beside painter-wave painter-diamond) simple-frame) "wave-beside-diamond")
+
 (display "\nex-2.51\n")
 
+; First implementation is at the beginning of this file.
+(draw-to-py ((corner-split painter-wave 4) simple-frame) "corner-split-4")
+(draw-to-py ((below painter-x painter-diamond) simple-frame) "x-below-diamond")
+
+
+
+
 (display "\nex-2.52\n")
 
 
diff --git a/picture_language/draw.scm b/picture_language/draw.scm
new file mode 100644
index 0000000..02518da
--- /dev/null
+++ b/picture_language/draw.scm
@@ -0,0 +1,26 @@
+(define (draw-to-py painter name)
+  (define py-name (string-append "picture_language/" name ".py"))
+  (define img-name (string-append name ".png"))
+  (define head (string-append
+    "from PIL import Image, ImageDraw\n"
+    "im = Image.new('RGB', (1921, 1081))\n"
+    "draw = ImageDraw.Draw(im)\n"))
+  (define tail (string-append
+    "im.save('" img-name "', 'PNG')\n"))
+  (let ((port (open-output-file py-name)))
+    (define (draw-line v1 v2)
+      (define n2s number->string)
+      (display
+        (string-append
+          "draw.line(("
+          (n2s (xcor-vect v1)) ", "
+          (n2s (ycor-vect v1)) ", "
+          (n2s (xcor-vect v2)) ", "
+          (n2s (ycor-vect v2)) "), "
+          "fill=128)\n") port))
+    (display head port)
+    (painter draw-line)
+    (display tail port)
+    (close-output-port port)))
+
+