[avr-libc-commit] [2331] Edited sun_rise() and sun_set() for clarity

[Mike Rice]

Revision: 2331
          http://svn.sv.gnu.org/viewvc/?view=rev&root=avr-libc&revision=2331
Author:   swfltek
Date:     2013-04-02 21:48:00 +0000 (Tue, 02 Apr 2013)
Log Message:
-----------
Edited sun_rise() and sun_set() for clarity

Modified Paths:
--------------
    trunk/avr-libc/libc/time/sun_rise.c
    trunk/avr-libc/libc/time/sun_set.c

Modified: trunk/avr-libc/libc/time/sun_rise.c
===================================================================
--- trunk/avr-libc/libc/time/sun_rise.c 2013-04-02 21:46:13 UTC (rev 2330)
+++ trunk/avr-libc/libc/time/sun_rise.c 2013-04-02 21:48:00 UTC (rev 2331)
@@ -29,7 +29,7 @@
 /* $Id$ */
 
 /*
-       Return the approximate time of sun rise.
+    Return the approximate time of sun rise.
 */
 
 #include <time.h>
@@ -38,19 +38,22 @@
 time_t
 sun_rise(time_t * timer)
 {
-       long            n;
-       time_t          t;
+    long            n;
+    time_t          t;
 
-       t = *timer % 86400UL;
-       t = *timer - t;
-       t += 43200L;
-       t -= equation_of_time(timer);
+    /* determine time of solar noon at the prime meridian */
+    t = *timer % ONE_DAY;
+    t = *timer - t;
+    t += 43200L;
+    t -= equation_of_time(timer);
 
-       n = daylight_seconds(timer) / 2L;
-       t -= n;
+    /* sunrise is 1/2 day earlier */
+    n = daylight_seconds(timer) / 2L;
+    t -= n;
 
-       n = __longitude / 15L;
-       t -= n;
+    /* rotate to observers longitude */
+    n = __longitude / 15L;
+    t -= n;
 
-       return t;
+    return t;
 }

Modified: trunk/avr-libc/libc/time/sun_set.c
===================================================================
--- trunk/avr-libc/libc/time/sun_set.c  2013-04-02 21:46:13 UTC (rev 2330)
+++ trunk/avr-libc/libc/time/sun_set.c  2013-04-02 21:48:00 UTC (rev 2331)
@@ -29,7 +29,7 @@
 /* $Id$ */
 
 /*
-       Return the approximate time of sun set.
+    Return the approximate time of sun set.
 */
 
 #include <time.h>
@@ -38,19 +38,22 @@
 time_t
 sun_set(time_t * timer)
 {
-       long            n;
-       time_t          t;
+    long            n;
+    time_t          t;
 
-       t = *timer % 86400UL;
-       t = *timer - t;
-       t += 43200L;
-       t -= equation_of_time(timer);
+     /* determine time of solar noon at the prime meridian */
+    t = *timer % ONE_DAY;
+    t = *timer - t;
+    t += 43200L;
+    t -= equation_of_time(timer);
 
-       n = daylight_seconds(timer) / 2L;
-       t += n;
+    /* sunset is 1/2 day earlier */
+    n = daylight_seconds(timer) / 2L;
+    t += n;
 
-       n = __longitude / 15L;
-       t -= n;
+     /* rotate to observers longitude */
+    n = __longitude / 15L;
+    t -= n;
 
-       return t;
+    return t;
 }