From 1fd2adc56bb2dc04eb4cef58403637d476b9819d Mon Sep 17 00:00:00 2001
From: John Honniball <coredump@virginmedia.com>
Date: Sat, 4 May 2019 20:07:34 +0100
Subject: [PATCH] New drawing: hexspiral, a hexagonal spiral. A turtle drawing,
 just for 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  |  1 +
 Makefile    | 11 ++++++++++-
 hexspiral.c | 25 +++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 hexspiral.c

diff --git a/.gitignore b/.gitignore
index c185140..c8ddba2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,6 +25,7 @@ flake
 fraserspiral
 hconic2
 hexagon
+hexspiral
 hilb
 hyp
 isogrid
diff --git a/Makefile b/Makefile
index 00b9143..73d5da4 100644
--- a/Makefile
+++ b/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
 
diff --git a/hexspiral.c b/hexspiral.c
new file mode 100644
index 0000000..ee7138c
--- /dev/null
+++ b/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);
+}