Split matrix-loops into separate do-for-cell macro

flora-search-aurora.lisp

@@ -35,75 +35,77 @@ Borrowed from https://github.com/gorozhin/chlorophyll/
   (format stream "~C[J" #\Esc))
 
 
+(defmacro do-for-cell (matrix &body body)
+  "Given a 2d-array (matrix), execute the body for every cell.
+The body has access to 4 variables:
+  * i/j — The current row/column.
+  * dimensions — Dimensions of the given matrix.
+  * cell — The value of the current cell."
+  `(let* ((dimensions (array-dimensions matrix))
+          (max-i (car dimensions))
+          (max-j (cadr dimensions))
+          (i 0)  (j 0))
+     (loop
+      (let ((cell (ignore-errors (aref matrix i j))))
+        (cond
+          ((< i max-i)
+           (cond
+             ((< j max-j)
+              ,@body
+              (incf j))
+             ((eq j max-j)
+              (setf j 0)
+              (incf i))))
+          ((eq i max-i)
+           (return)))))))
+
+
 (defun matrix-delta (a b)
   "Given two 2D matrices, return a listcontaining on the cells that change between a→b in the following
 format:
 only the cells that change between a→b — all others are nil."
-  (let* ((dimensions (array-dimensions a))
-         (delta (make-array dimensions :initial-element nil))
-         (max-i (car dimensions))
-         (max-j (cadr dimensions))
-         (i 0)  (j 0))
-    (loop
-     (cond
-       ((< i max-i)
-        (cond
-          ((< j max-j)
-           (if (not (eq (aref a i j)
+  (let ((delta (make-array (array-dimensions a))))
+    (do-for-cell a
+      (when (not (eq cell
                      (aref b i j)))
           (setf (aref delta i j)
-                     (aref b i j)))
-           (incf j))
-          ((eq j max-j)
-           (setf j 0)
-           (incf i))))
-       ((eq i max-i)
-        (return))))
+                (aref b i j))))
     delta))
 
 
-(defun print-screen-matrix (array)
+(defun print-screen-matrix (matrix)
   "Given a matrix of characters, print each element to standard output."
-  (let* ((dimensions (array-dimensions array))
-         (max-i (car dimensions))
-         (max-j (cadr dimensions))
-         (i 0)  (j 0))
-    (loop
-     (cond
-       ((< i max-i)
-        (cond
-          ((< j max-j)
-           (if (characterp (aref array i j))
-               (progn
-                 (move-cursor i j)
-                 (write-char (aref array i j))))
-           (incf j))
-          ((eq j max-j)
-           (setf j 0)
-           (incf i))))
-       ((eq i max-i)
-        (return))))))
+  (do-for-cell matrix
+    (when (characterp cell)
+      (move-cursor (+ i 1) (+ j 1))
+      (write-char cell))))
 
 
-(defun screen-matrix-set-map (array map-path)
+(defun make-screen-matrix ()
+  "Create a “screen matrix” — that is, a 2D array representing the
+72x20 grid of characters we can print to the terminal."
+  (make-array '(20 72) :initial-element #\space))
+
+
+(defun screen-matrix-set-map (matrix map-path)
   "Draw a Tiled-format tilemap to the 2D array."
-  (mapcar (lambda (layer) (screen-matrix-set-map-layer array layer))
+  (mapcar (lambda (layer) (screen-matrix-set-map-layer matrix layer))
           (cl-tiled:map-layers (cl-tiled:load-map map-path)))
-  array)
+  matrix)
 
 
-(defun screen-matrix-set-map-layer (array tile-layer)
+(defun screen-matrix-set-map-layer (matrix tile-layer)
   "Set an array's elements to those corresponding the given Tiled
 tile-layer's cells. a Tiled tile-layer to the screen."
-  (mapcar (lambda (cell) (screen-matrix-set-char-cell array cell))
+  (mapcar (lambda (cell) (screen-matrix-set-char-cell matrix cell))
           (cl-tiled:layer-cells tile-layer))
-  array)
+  matrix)
 
 
-(defun screen-matrix-set-char-cell (array cell)
-  "Set a 2D array's element corresponding to a Tiled cell's
-character-value, using it's column and row."
-  (setf (aref array
+(defun screen-matrix-set-char-cell (matrix cell)
+  "Set a matrice's (2d array's) element corresponding to
+a Tiled cell's character-value, using it's column and row."
+  (setf (aref matrix
               (cl-tiled:cell-row cell)
               (cl-tiled:cell-column cell))
         (tile-character
@@ -118,5 +120,3 @@ with 15 characters-per-line."
    (+ (* (cl-tiled:tile-row tile) 15)
       (cl-tiled:tile-column tile)
       32)))
-
-(main)