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Task/Xiaolin-Wus-line-algorithm/Sidef/xiaolin-wus-line-algorithm.sidef

@@ -0,0 +1,58 @@
+func plot(x, y, c) {
+    c && printf("plot %d %d %.1f\n", x, y, c);
+}
+
+func fpart(x) {
+    x - int(x);
+}
+
+func rfpart(x) {
+    1 - fpart(x);
+}
+
+func drawLine(x0, y0, x1, y1) {
+
+    var p = plot;
+    if (abs(y1 - y0) > abs(x1 - x0)) {
+        p = {|arg| plot(arg[1, 0, 2]) };
+        (x0, y0, x1, y1) = (y0, x0, y1, x1);
+    }
+
+    if (x0 > x1) {
+        (x0, x1, y0, y1) = (x1, x0, y1, y0);
+    }
+
+    var dx = (x1 - x0);
+    var dy = (y1 - y0);
+    var gradient = (dy / dx);
+
+    var xends = [];
+    var intery;
+
+    # handle the endpoints
+    for x,y in [[x0, y0], [x1, y1]] {
+        var xend = int(x + 0.5);
+        var yend = (y + gradient*(xend-x));
+        var xgap = rfpart(x + 0.5);
+
+        var x_pixel = xend;
+        var y_pixel = yend.int;
+        xends << x_pixel;
+
+        p.call(x_pixel, y_pixel  , rfpart(yend) * xgap);
+        p.call(x_pixel, y_pixel+1,  fpart(yend) * xgap);
+        defined(intery) && next;
+
+        # first y-intersection for the main loop
+        intery = (yend + gradient);
+    }
+
+    # main loop
+    range(xends[0]+1, xends[1]-1).each { |x|
+        p.call(x, intery.int,  rfpart(intery));
+        p.call(x, intery.int+1, fpart(intery));
+        intery += gradient;
+    }
+}
+
+drawLine(0, 1, 10, 2);