Update pom to the third edition of Duffett-Smith's book, and clean it

up somewhat.  Change time specification format to similar to that used
by date(1) - taking a command line argument in seconds since the Epoch
is silly.  Date parsing based on code from date(1).

Based on work by Paul Janzen for OpenBSD.

2 files changed, 155 insertions, 57 deletions

diff --git a/pom/pom.6 b/pom/pom.6
index 4a4ce04a..42f663d7 100644
--- a/pom/pom.6
+++ b/pom/pom.6
@@ -1,4 +1,4 @@
-.\"	$NetBSD: pom.6,v 1.6 1998/06/13 01:09:22 jeremy Exp $
+.\"	$NetBSD: pom.6,v 1.7 1999/09/14 20:00:07 jsm Exp $
 .\"
 .\" Copyright (c) 1989, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -33,7 +33,7 @@
 .\"
 .\"	@(#)pom.6	8.1 (Berkeley) 5/31/93
 .\"
-.Dd May 31, 1993
+.Dd January 9, 1999
 .Dt POM 6
 .Os
 .Sh NAME
@@ -41,7 +41,7 @@
 .Nd display the phase of the moon
 .Sh SYNOPSIS
 .Nm
-.Op Ar secs
+.Op [[[[[cc]yy]mm]dd]HH]
 .Sh DESCRIPTION
 The
 .Nm
@@ -49,13 +49,25 @@ utility displays the current phase of the moon.
 Useful for selecting software completion target dates and predicting 
 managerial behavior.
 .Pp
-.Bl -tag -width secs
-.It Ar secs
-Display the phase of the moon for the date represented by
-.Ar secs
-seconds past the Epoch
-(Midnight, January 1, 1970 GMT).
-If
-.Ar secs
-is unspecified, the current time is used.
+.Bl -tag -width [[[[[cc]yy]mm]dd]HH]
+.It Ar [[[[[cc]yy]mm]dd]HH]
+Display the phase of the moon for a given time.  The format is similar to
+the canonical representation used by
+.Xr date 1 .
 .El
+.Sh SEE ALSO
+.Xr date 1
+.Sh AUTHOR
+.Nm
+was written by Keith E. Brandt.
+.Sh BUGS
+Times must be within range of the
+.Ux
+epoch.
+.Pp
+This program does not allow for the difference between the TDT and
+UTC timescales (about one minute at the time of writing).
+.Sh ACKNOWLEDGEMENTS
+This program is based on algorithms from
+.%B Practical Astronomy with Your Calculator, Third Edition
+by Peter Duffett-Smith <pjds@mrao.cam.ac.uk>.
diff --git a/pom/pom.c b/pom/pom.c
index 050c937a..97a946d4 100644
--- a/pom/pom.c
+++ b/pom/pom.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: pom.c,v 1.11 1998/09/11 14:07:04 hubertf Exp $	*/
+/*	$NetBSD: pom.c,v 1.12 1999/09/14 20:00:07 jsm Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -45,7 +45,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
 #if 0
 static char sccsid[] = "@(#)pom.c	8.1 (Berkeley) 5/31/93";
 #else
-__RCSID("$NetBSD: pom.c,v 1.11 1998/09/11 14:07:04 hubertf Exp $");
+__RCSID("$NetBSD: pom.c,v 1.12 1999/09/14 20:00:07 jsm Exp $");
 #endif
 #endif /* not lint */
 
@@ -57,60 +57,71 @@ __RCSID("$NetBSD: pom.c,v 1.11 1998/09/11 14:07:04 hubertf Exp $");
  *
  * -- Keith E. Brandt  VIII 1984
  *
+ * Updated to the Third Edition of Duffett-Smith's book, Paul Janzen, IX 1998
+ *
  */
 
-#include <sys/time.h>
+#include <ctype.h>
 #include <err.h>
-#include <errno.h>
 #include <math.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
-#include <tzfile.h>
+#include <time.h>
+#include <unistd.h>
 
 #ifndef PI
 #define	PI	  3.14159265358979323846
 #endif
-#define	EPOCH	  85		/* really 1985 */
-#define	EPSILONg  279.611371	/* solar ecliptic long at EPOCH */
-#define	RHOg	  282.680403	/* solar ecliptic long of perigee at EPOCH */
-#define	ECCEN	  0.01671542	/* solar orbit eccentricity */
-#define	lzero	  18.251907	/* lunar mean long at EPOCH */
-#define	Pzero	  192.917585	/* lunar mean long of perigee at EPOCH */
-#define	Nzero	  55.204723	/* lunar mean long of node at EPOCH */
+
+/*
+ * The EPOCH in the third edition of the book is 1990 Jan 0.0 TDT.
+ * In this program, we do not bother to correct for the differences
+ * between UTC (as shown by the UNIX clock) and TDT.  (TDT = TAI + 32.184s;
+ * TAI-UTC = 32s in Jan 1999.)
+ */
+#define EPOCH_MINUS_1970	(20 * 365 + 5 - 1) /* 20 years, 5 leaps, back 1 day to Jan 0 */
+#define	EPSILONg  279.403303	/* solar ecliptic long at EPOCH */
+#define	RHOg	  282.768422	/* solar ecliptic long of perigee at EPOCH */
+#define	ECCEN	  0.016713	/* solar orbit eccentricity */
+#define	lzero	  318.351648	/* lunar mean long at EPOCH */
+#define	Pzero	  36.340410	/* lunar mean long of perigee at EPOCH */
+#define	Nzero	  318.510107	/* lunar mean long of node at EPOCH */
 
 void	adj360 __P((double *));
 double	dtor __P((double));
 int	main __P((int, char *[]));
 double	potm __P((double));
+time_t	parsetime __P((char *));
+void	badformat __P((void)) __attribute__((__noreturn__));
 
 int
 main(argc, argv)
 	int argc;
 	char *argv[];
 {
-	struct timeval tp;
-	struct timezone tzp;
-	struct tm *GMT;
-	time_t tmpt;
+	time_t tmpt, now;
 	double days, today, tomorrow;
-	int cnt;
+	char buf[1024];
 
+	if (time(&now) == (time_t)-1)
+		err(1, "time");
 	if (argc > 1) {
-		tp.tv_sec = atoi(argv[1]);
-		tp.tv_usec = 0;
+		tmpt = parsetime(argv[1]);
+		strftime(buf, sizeof(buf), "%a %Y %b %e %H:%M:%S (%Z)",
+			localtime(&tmpt));
+		printf("%s:  ", buf);
 	} else {
-		if (gettimeofday(&tp,&tzp))
-			err(1, "gettimeofday");
+		tmpt = now;
 	}
-	tmpt = tp.tv_sec;
-	GMT = gmtime(&tmpt);
-	days = (GMT->tm_yday + 1) + ((GMT->tm_hour +
-	    (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0);
-	for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
-		days += isleap(cnt + 1900) ? 366 : 365;
+	days = (tmpt - EPOCH_MINUS_1970 * 86400) / 86400.0;
 	today = potm(days) + .5;
-	(void)printf("The Moon is ");
+	if (tmpt < now)
+		(void)printf("The Moon was ");
+	else if (tmpt == now)
+		(void)printf("The Moon is ");
+	else
+		(void)printf("The Moon will be ");
 	if ((int)today == 100)
 		(void)printf("Full\n");
 	else if (!(int)today)
@@ -120,7 +131,11 @@ main(argc, argv)
 		if ((int)today == 50)
 			(void)printf("%s\n", tomorrow > today ?
 			    "at the First Quarter" : "at the Last Quarter");
+			/* today is 0.5 too big, but it doesn't matter here
+			 * since the phase is changing fast enough
+			 */
 		else {
+			today -= 0.5;		/* Now it might matter */
 			(void)printf("%s ", tomorrow > today ?
 			    "Waxing" : "Waning");
 			if (today > 50)
@@ -145,30 +160,30 @@ potm(days)
 	double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
 	double A4, lprime, V, ldprime, D, Nm;
 
-	N = 360 * days / 365.2422;				/* sec 42 #3 */
+	N = 360 * days / 365.242191;				/* sec 46 #3 */
 	adj360(&N);
-	Msol = N + EPSILONg - RHOg;				/* sec 42 #4 */
+	Msol = N + EPSILONg - RHOg;				/* sec 46 #4 */
 	adj360(&Msol);
-	Ec = 360 / PI * ECCEN * sin(dtor(Msol));		/* sec 42 #5 */
-	LambdaSol = N + Ec + EPSILONg;				/* sec 42 #6 */
+	Ec = 360 / PI * ECCEN * sin(dtor(Msol));		/* sec 46 #5 */
+	LambdaSol = N + Ec + EPSILONg;				/* sec 46 #6 */
 	adj360(&LambdaSol);
-	l = 13.1763966 * days + lzero;				/* sec 61 #4 */
+	l = 13.1763966 * days + lzero;				/* sec 65 #4 */
 	adj360(&l);
-	Mm = l - (0.1114041 * days) - Pzero;			/* sec 61 #5 */
+	Mm = l - (0.1114041 * days) - Pzero;			/* sec 65 #5 */
 	adj360(&Mm);
-	Nm = Nzero - (0.0529539 * days);			/* sec 61 #6 */
+	Nm = Nzero - (0.0529539 * days);			/* sec 65 #6 */
 	adj360(&Nm);
-	Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm));	/* sec 61 #7 */
-	Ac = 0.1858 * sin(dtor(Msol));				/* sec 61 #8 */
+	Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm));	/* sec 65 #7 */
+	Ac = 0.1858 * sin(dtor(Msol));				/* sec 65 #8 */
 	A3 = 0.37 * sin(dtor(Msol));
-	Mmprime = Mm + Ev - Ac - A3;				/* sec 61 #9 */
-	Ec = 6.2886 * sin(dtor(Mmprime));			/* sec 61 #10 */
-	A4 = 0.214 * sin(dtor(2 * Mmprime));			/* sec 61 #11 */
-	lprime = l + Ev + Ec - Ac + A4;				/* sec 61 #12 */
-	V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));	/* sec 61 #13 */
-	ldprime = lprime + V;					/* sec 61 #14 */
-	D = ldprime - LambdaSol;				/* sec 63 #2 */
-	return(50 * (1 - cos(dtor(D))));			/* sec 63 #3 */
+	Mmprime = Mm + Ev - Ac - A3;				/* sec 65 #9 */
+	Ec = 6.2886 * sin(dtor(Mmprime));			/* sec 65 #10 */
+	A4 = 0.214 * sin(dtor(2 * Mmprime));			/* sec 65 #11 */
+	lprime = l + Ev + Ec - Ac + A4;				/* sec 65 #12 */
+	V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));	/* sec 65 #13 */
+	ldprime = lprime + V;					/* sec 65 #14 */
+	D = ldprime - LambdaSol;				/* sec 67 #2 */
+	return(50.0 * (1 - cos(dtor(D))));			/* sec 67 #3 */
 }
 
 /*
@@ -198,3 +213,74 @@ adj360(deg)
 		else
 			break;
 }
+
+#define	ATOI2(ar)	((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;
+time_t
+parsetime(p)
+	char *p;
+{
+	struct tm *lt;
+	int bigyear;
+	int yearset = 0;
+	time_t tval;
+	unsigned char *t;
+	
+	for (t = p; *t; ++t) {
+		if (isdigit(*t))
+			continue;
+		badformat();
+	}
+
+	tval = time(NULL);
+	lt = localtime(&tval);
+	lt->tm_sec = 0;
+	lt->tm_min = 0;
+
+	switch (strlen(p)) {
+	case 10:				/* yyyy */
+		bigyear = ATOI2(p);
+		lt->tm_year = bigyear * 100 - 1900;
+		yearset = 1;
+		/* FALLTHROUGH */
+	case 8:					/* yy */
+		if (yearset) {
+			lt->tm_year += ATOI2(p);
+		} else {
+			lt->tm_year = ATOI2(p);
+			if (lt->tm_year < 69)		/* hack for 2000 */
+				lt->tm_year += 100;
+		}
+		/* FALLTHROUGH */
+	case 6:					/* mm */
+		lt->tm_mon = ATOI2(p);
+		if ((lt->tm_mon > 12) || !lt->tm_mon)
+			badformat();
+		--lt->tm_mon;			/* time struct is 0 - 11 */
+		/* FALLTHROUGH */
+	case 4:					/* dd */
+		lt->tm_mday = ATOI2(p);
+		if ((lt->tm_mday > 31) || !lt->tm_mday)
+			badformat();
+		/* FALLTHROUGH */
+	case 2:					/* HH */
+		lt->tm_hour = ATOI2(p);
+		if (lt->tm_hour > 23)
+			badformat();
+		break;
+	default:
+		badformat();
+	}
+	/* The calling code needs a valid tm_ydays and this is the easiest
+	 * way to get one */
+	if ((tval = mktime(lt)) == -1)
+		errx(1, "specified date is outside allowed range");
+	return (tval);
+}
+
+void
+badformat()
+{
+	warnx("illegal time format");
+	(void)fprintf(stderr, "usage: pom [[[[[cc]yy]mm]dd]HH]\n");
+	exit(1);
+}