From a1266ca648d55d9b6b90f9ac3309a26e5d1e3c68 Mon Sep 17 00:00:00 2001
From: MsK` <msk@lywenn.eu.org>
Date: Sat, 11 Dec 2021 10:30:24 +0100
Subject: [PATCH] factorized heightmap code into matrix code, and using records
 now

---
 09-smoke-basin/code.scm | 61 ++++++++++-------------------------------
 common.scm              | 26 ++++++++++++++++++
 2 files changed, 40 insertions(+), 47 deletions(-)

diff --git a/09-smoke-basin/code.scm b/09-smoke-basin/code.scm
index ae6d85b..f791ab6 100644
--- a/09-smoke-basin/code.scm
+++ b/09-smoke-basin/code.scm
@@ -1,39 +1,6 @@
 (import (srfi :43)) ; vector extensions
 (load "../common.scm")
 
-; constructor of heightmap object
-; from a vector of vector of altitudes
-(define (make-heightmap data)
-  (list
-    (vector-length (vector-ref data 0)) ; width
-    (vector-length data) ; height
-    data))
-
-; heightmap object getters
-(define (heightmap-width heightmap) (car heightmap))
-(define (heightmap-height heightmap) (cadr heightmap))
-(define (heightmap-data heightmap) (caddr heightmap))
-(define (sample-heightmap heightmap x y)
-  (if (or (< x 0)
-	  (< y 0)
-	  (>= x (heightmap-width heightmap))
-	  (>= y (heightmap-height heightmap)))
-    9
-    (vector-ref (vector-ref (heightmap-data heightmap) y) x)))
-
-; parse altitude data from file and return an heightmap object
-(define (load-heightmap file)
-  (let y-loop [(heightmap '())]
-    (let x-loop [(line '())]
-      (let [(c (get-char file))]
-	(cond
-	  [(eof-object? c)
-	   (make-heightmap (reverse-list->vector heightmap))]
-	  [(char-whitespace? c)
-	   (y-loop (cons (reverse-list->vector line) heightmap))]
-	  [(char-numeric? c)
-	   (x-loop (cons (char->number c) line))])))))
-
 ; constructor of low point objects
 ; from their position and altitude
 (define (make-low-point x y altitude)
@@ -50,17 +17,17 @@
       (lambda (y line)
 	(vector-for-each
 	  (lambda (x altitude)
-	    (let [(left (sample-heightmap heightmap (- x 1) y))
-		  (right (sample-heightmap heightmap (+ x 1) y))
-		  (up (sample-heightmap heightmap x (- y 1)))
-		  (down (sample-heightmap heightmap x (+ y 1)))]
+	    (let [(left (matrix-get heightmap (- x 1) y))
+		  (right (matrix-get heightmap (+ x 1) y))
+		  (up (matrix-get heightmap x (- y 1)))
+		  (down (matrix-get heightmap x (+ y 1)))]
 	      (when (and (< altitude left)
 			 (< altitude right)
 			 (< altitude up)
 			 (< altitude down))
 		(set! low-points (cons (make-low-point x y altitude) low-points)))))
 	  line))
-      (heightmap-data heightmap))
+      (matrix-data heightmap))
     low-points))
 
 ; compute risk level from low point list
@@ -70,8 +37,8 @@
 ; starting with from a given low-point
 ; call closure with and all points of the corresponding basin
 (define (visit-basin heightmap low-point closure)
-  (let* [(width (heightmap-width heightmap))
-	 (height (heightmap-height heightmap))
+  (let* [(width (matrix-width heightmap))
+	 (height (matrix-height heightmap))
 	 (width-1 (- width 1))
 	 (height-1 (- height 1))
 	 (visited (make-vector (* width height) 0))]
@@ -82,7 +49,7 @@
       (let [(ofs (offset x y))]
 	(when (= (vector-ref visited ofs) 0)
 	  (vector-set! visited ofs 1)
-	  (when (< (sample-heightmap heightmap x y) 9)
+	  (when (< (matrix-get heightmap x y) 9)
 	    (closure x y)
 	    (when (> x 0)        (flood-fill (- x 1) y))
 	    (when (< x width-1)  (flood-fill (+ x 1) y))
@@ -118,12 +85,12 @@
     (lambda (file)
       ; write header to file: "P3" followed by width, height and max value of channel
       (fprintf file "P3~%~a ~a~%255~%"
-	       (heightmap-width heightmap)
-	       (heightmap-height heightmap))
+	       (matrix-width heightmap)
+	       (matrix-height heightmap))
 
-      (let* [(width (heightmap-width heightmap))
+      (let* [(width (matrix-width heightmap))
 	     (width*3 (* width 3))
-	     (height (heightmap-height heightmap))
+	     (height (matrix-height heightmap))
 	     (data (make-vector (* width*3 width)))]
 
 	; from (x,y) returns of offset of pixel's red channel in data vector
@@ -136,7 +103,7 @@
 	(let y-loop [(y 0)]
 	  (let x-loop [(x 0)]
 	    (let [(ofs (offset x y))
-		  (gray-level (* (sample-heightmap heightmap x y) 20))]
+		  (gray-level (* (matrix-get heightmap x y) 20))]
 	      ; red channel
 	      (vector-set! data ofs gray-level)
 	      ; green channel
@@ -173,7 +140,7 @@
 (call-with-input-file
   "input"
   (lambda (file)
-    (let* [(heightmap (load-heightmap file))
+    (let* [(heightmap (load-matrix file))
 	   (low-points (find-low-points heightmap))]
       (printf "part 1:~% Risk level: ~a~%"
 	      (risk-level low-points))
diff --git a/common.scm b/common.scm
index e21f5c2..32916a2 100644
--- a/common.scm
+++ b/common.scm
@@ -12,3 +12,29 @@
 (define (char->number c)
   (- (char->integer c) 48)) ; 48 is ASCII's number zero
 
+(define-record-type matrix (fields width height data))
+(define (matrix-get matrix x y)
+  (if (or (< x 0)
+	  (< y 0)
+	  (>= x (matrix-width matrix))
+	  (>= y (matrix-height matrix)))
+    9
+    (vector-ref (vector-ref (matrix-data matrix) y) x)))
+(define (matrix-from-data data)
+  (make-matrix
+    (vector-length (vector-ref data 0))
+    (vector-length data)
+    data))
+
+; parse 0-9 numerical data from file and return a matrix
+(define (load-matrix file)
+  (let y-loop [(heightmap '())]
+    (let x-loop [(line '())]
+      (let [(c (get-char file))]
+	(cond
+	  [(eof-object? c)
+	   (matrix-from-data (reverse-list->vector heightmap))]
+	  [(char-whitespace? c)
+	   (y-loop (cons (reverse-list->vector line) heightmap))]
+	  [(char-numeric? c)
+	   (x-loop (cons (char->number c) line))])))))