From f339c929c59fa42e5718ae40309bee3c5f7af24e Mon Sep 17 00:00:00 2001
From: John Honniball <coredump@virginmedia.com>
Date: Sat, 30 Jun 2018 00:56:18 +0100
Subject: [PATCH] Update for new coding standards. Fix header comment. Rename a
 couple of variables.

---
 pappus.c | 53 +++++++++++++++++++++++++----------------------------
 1 file changed, 25 insertions(+), 28 deletions(-)

diff --git a/pappus.c b/pappus.c
index 7b18b89..4932387 100644
--- a/pappus.c
+++ b/pappus.c
@@ -1,5 +1,5 @@
 /* pappus --- draw the Pappus Chain on the plotter          2011-06-01 */
-/* Copyright (c) 2011 John Honniball, Dorkbot Bristol                  */
+/* Copyright (c) 2011 John Honniball, Froods Software Development      */
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -7,11 +7,11 @@
 #include <math.h>
 #include "hpgllib.h"
 
-double pappus_circle (double x0, double y0, double x, double y, double rad);
+double pappus_circle(const double x0, const double y0, double x, double y, const double rad);
 
-double Rad;
+double Ycentre;
 
-int main (int argc, char * const argv[])
+int main(int argc, char * const argv[])
 {
    int opt;
    double xc, yc;
@@ -20,11 +20,11 @@ int main (int argc, char * const argv[])
    double r;
    double r2;
    double rad;
-   double csize;
+   double csize_mm;
    int n;
    int n2;
    
-   while ((opt = getopt (argc, argv, "no:p:s:t:v:")) != -1) {
+   while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {
       switch (opt) {
       case 'n':
       case 'o':
@@ -32,41 +32,38 @@ int main (int argc, char * const argv[])
       case 's':
       case 't':
       case 'v':
-         plotopt (opt, optarg);
+         plotopt(opt, optarg);
          break;
       default: /* '?' */
-         fprintf (stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n",
+         fprintf(stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n",
                   argv[0]);
-         fprintf (stderr, "       <size> ::= A1 | A2 | A3 | A4 | A5\n");
-//       exit (EXIT_FAILURE);
+         fprintf(stderr, "       <size> ::= A1 | A2 | A3 | A4 | A5\n");
+//       exit(EXIT_FAILURE);
       }
    }
 
-   plotbegin (0);
+   plotbegin(0);
 
-   getplotsize (&maxx, &maxy);
+   getplotsize(&maxx, &maxy);
    
    xc = maxx / 2.0;
    yc = maxy / 2.0;
    
-   Rad = yc;
+   Ycentre = yc;
    
    /* Just draw with pen 1 for now. Maybe change pens half-way */
-   pencolr (0);
+   pencolr(0);
 
    /* Draw outermost circle as large as will fit on a page */
-   circle (xc, yc, Rad);
+   circle(xc, yc, yc);
    
    /* For an explanation of the mathematics of the Pappus
     * Chain, see Wikipedia: http://en.wikipedia.org/wiki/Pappus_chain
     */
 
-// r = 2.0 / 3.0;
    r = 1.0 / 2.0;
    n = 0;
    
-   /* pappus_circle ((1.0 - r) / 2.0, 0.0, (1.0 - r) / 2.0); */
-   
    do {
       n2 = n * n;
       r2 = (1.0 - r) * (1.0 - r);
@@ -75,12 +72,12 @@ int main (int argc, char * const argv[])
       y = (n * r * (1.0 - r)) / ((n2 * r2) + r);
       rad = ((1.0 - r) * r) / (2.0 * ((n2 * r2) + r));
       
-//    fprintf (stderr, "n = %d, x = %f, y = %f, rad = %f\n", n, x, y, rad);
+//    fprintf(stderr, "n = %d, x = %f, y = %f, rad = %f\n", n, x, y, rad);
       
-      csize = pappus_circle (xc, yc, x * maxy, y * maxy, rad * maxy);
+      csize_mm = pappus_circle(xc, yc, x * maxy, y * maxy, rad * maxy);
       
       n++;
-   } while (csize > 1.5);
+   } while (csize_mm > 1.5);
    
    /* Again, with the circles reflected. Repeating the entire sequence
     * results in less wasted pen movement and hence faster plotting
@@ -96,25 +93,25 @@ int main (int argc, char * const argv[])
       y = (n * r * (1.0 - r)) / ((n2 * r2) + r);
       rad = ((1.0 - r) * r) / (2.0 * ((n2 * r2) + r));
       
-//    fprintf (stderr, "n = %d, x = %f, y = %f, rad = %f\n", n, x, y, rad);
+//    fprintf(stderr, "n = %d, x = %f, y = %f, rad = %f\n", n, x, y, rad);
       
-      csize = pappus_circle (xc, yc, (1.0 - x) * maxy, -y * maxy, rad * maxy);
+      csize_mm = pappus_circle(xc, yc, (1.0 - x) * maxy, -y * maxy, rad * maxy);
       
       n++;
-   } while (csize > 1.5);
+   } while (csize_mm > 1.5);
    
-   plotend ();
+   plotend();
 
    exit (0);
 }
 
 
-double pappus_circle (double x0, double y0, double x, double y, double rad)
+double pappus_circle(const double x0, const double y0, double x, double y, const double rad)
 {
-   x += x0 - Rad;
+   x += x0 - Ycentre;
    y += y0;
    
-   circle (x, y, rad);
+   circle(x, y, rad);
    
    return ((rad * 2.0) / 40.0);
 }