New drawing: hexspiral, a hexagonal spiral. A turtle drawing, just fo…

…r a change. Not yet able to scale up for the big plotters, but should be the right size for A3. Would look nice in six colours, but would be much slower with all those pen changes.

.gitignore

@@ -25,6 +25,7 @@ flake
 fraserspiral
 hconic2
 hexagon
+hexspiral
 hilb
 hyp
 isogrid

Makefile

@@ -20,7 +20,7 @@ HPGL=flake.hpgl op.hpgl dala1.hpgl hconic2.hpgl tree.hpgl dome.hpgl \
      curve_stitching.hpgl cs_rosette.hpgl allover13.hpgl allover12.hpgl \
      qrplot.hpgl lotus.hpgl celticstep.hpgl op_moire.hpgl sutpent.hpgl \
      morphpoly.hpgl pin_circle.hpgl isogrid.hpgl circle_lines.hpgl \
-     star_grid.hpgl ternary_arcs.hpgl
+     star_grid.hpgl ternary_arcs.hpgl hexspiral.hpgl
 
 PNG=$(HPGL:.hpgl=.png)
 
@@ -385,6 +385,15 @@ hexagon: hexagon.o turtle.o
 hexagon.o: hexagon.c turtle.h
 	$(CC) $(CFLAGS) -o $@ hexagon.c
 
+hexspiral.hpgl: hexspiral
+	./hexspiral >hexspiral.hpgl
+
+hexspiral: hexspiral.o turtle.o
+	$(LD) -o $@ hexspiral.o turtle.o -lm
+
+hexspiral.o: hexspiral.c turtle.h
+	$(CC) $(CFLAGS) -o $@ hexspiral.c
+
 plottext: plottext.o turtle.o
 	$(LD) -o $@ plottext.o turtle.o -lm
 

hexspiral.c

@@ -0,0 +1,25 @@
+/* hexspiral --- plot a hexagonal spiral                    2019-05-04 */
+/* Copyright (c) 2019 John Honniball, Froods Software Development      */
+
+#include <stdio.h>
+#include "turtle.h"
+
+int main(int argc, const char *argv[])
+{
+   int i;
+
+   turtle(DEV_HPGL, SIZ_A4, ORI_LAND, FLG_BORD);
+
+   colour(BLACK);
+
+   pen(DOWN);
+
+   for (i = 1; i < 360; i++) {
+      forward((double)i / 4.0);
+      turn(59.0);
+   }
+
+   show();
+
+   return (0);
+}