Not working at the moment

sudoku.lispbm

@@ -38,6 +38,14 @@
         (_ (cons e (repeat (- x 1) e))))
     'error))
 
+(defun replace (lst i e)
+  (match lst
+         (((?x) . (?xs)) (match i
+                                (0 (cons e xs))
+                                (_ (cons x (replace xs (- i 1) e)))))
+         (nil nil)))
+
+
 (defun valid (x)
     (if (= 9 (length x))
         (foldr
@@ -90,6 +98,10 @@
         ('error)))
     (_ 'error)))
 
+(defun place (m r c e)
+  (let ((row (getRow m r)) (updatedRow (replace row c e)))
+    (replace m r updatedRow)))
+
 (defun getCol (grid x) (getRow (transpose grid) x))
 
 (defun MatrixToList (m) (foldr append nil m))
@@ -106,3 +118,24 @@
             (ec (+ sc 2)))
         (matrixToList (getSubMatrix m sr er sc ec)))
       'error))
+
+(defun solve (grid)
+  (let ((empties (findEmpty grid))
+        (size1 (foldr
+                  (lambda (x ys)
+                    (let ((e (match x
+                                (((?r) (?c)) (notPresent r c)))))
+                        (if (= 1 (length e))
+                            (cons (append e x) ys)
+                            ys)))
+                  nil
+                  empties)))
+    (if (eq empties nil)
+        grid
+        (if (eq size1 nil)
+            () ; TODO: Empty
+            (solve (foldr (lambda (x gs)
+                     (match x
+                        ((?e) (?r) (?c)) (place g r c e)))
+                   grid size1))
+           ))))