Added another C example program: positions.c.

This example demonstrates how to calculate equatorial coordinates
and horizontal coordinates of solar system bodies.

Added explanatory comments to moonphase.c.

Added #defines for MIN_YEAR, MAX_YEAR in astronomy.h.

Removed unnecessary code from positions.html; no longer need
to calculate geocentric vector before calculating equatorial coordinates.

demo/browser/positions.html

@@ -206,7 +206,6 @@
 
                     for (let body of Astronomy.Bodies) {
                         if (body !== 'Earth') {
-                            let gv = Astronomy.GeoVector(body, date);
                             let equ_2000 = Astronomy.Equator(body, date, observer, false, true);
                             let equ_ofdate = Astronomy.Equator(body, date, observer, true, true);
                             let hor = Astronomy.Horizon(date, observer, equ_ofdate.ra, equ_ofdate.dec, 'normal');

demo/c/README.md

@@ -6,6 +6,11 @@
 This example shows how to determine the Moon's current phase,
 and how to predict when the next few quarter phases will occur.
 
+### [Body Positions](https://github.com/cosinekitty/astronomy/blob/master/demo/c/positions.c)
+An example of how to calculate equatorial and horizontal coordinates for all of the major solar system bodies.
+
+---
+
 # [API Reference](../../source/c/)
 Complete documentation for all the functions and types available
 in the C version of Astronomy Engine.

demo/c/astro_demo_common.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include "astronomy.h"
+
+int ParseArgs(int argc, const char *argv[], astro_observer_t *observer, astro_time_t *time)
+{
+    if (argc == 3 || argc == 4)
+    {
+        observer->height = 0.0;
+
+        if (1 != sscanf(argv[1], "%lf", &observer->latitude) || 
+            observer->latitude < -90.0 || 
+            observer->latitude > +90.0)
+        {
+            fprintf(stderr, "ERROR: Invalid latitude '%s' on command line\n", argv[1]);
+            return 1;
+        }
+
+        if (1 != sscanf(argv[2], "%lf", &observer->longitude) ||
+            observer->longitude < -180.0 ||
+            observer->longitude > +180.0)
+        {
+            fprintf(stderr, "ERROR: Invalid longitude '%s' on command line\n", argv[2]);
+            return 1;
+        }
+
+        if (argc == 4)
+        {
+            /* Time is present on command line, so use it. */
+
+            astro_utc_t utc;
+            int nscanned = sscanf(argv[3], "%d-%d-%dT%d:%d:%lfZ",
+                &utc.year, &utc.month, &utc.day,
+                &utc.hour, &utc.minute, &utc.second);
+
+            if (nscanned != 6)
+            {
+                fprintf(stderr, "ERROR: Invalid date/time format in '%s'\n", argv[3]);
+                return 1;
+            }
+
+            *time = Astronomy_TimeFromUtc(utc);
+        }
+        else
+        {
+            /* Time is absent on command line, so use current time. */
+            *time = Astronomy_CurrentTime();
+        }
+        return 0;
+    }
+
+    fprintf(stderr, "USAGE: %s latitude longitude [yyyy-mm-ddThh:mm:ssZ]\n", argv[0]);
+    return 1;
+}

demo/c/astro_demo_common.h

@@ -0,0 +1,7 @@
+#ifndef __ASTRONOMY_DEMO_COMMON_H
+#define __ASTRONOMY_DEMO_COMMON_H
+#include "astronomy.h"
+
+int ParseArgs(int argc, const char *argv[], astro_observer_t *observer, astro_time_t *time);
+
+#endif /* __ASTRONOMY_DEMO_COMMON_H */

demo/c/moonphase.c

@@ -3,6 +3,9 @@
 
     Example C program for Astronomy Engine:
     https://cosinekitty.github.io/astronomy/
+
+    This program calculates the Moon's phase for the current date and time.
+    It also finds the dates and times of the next 10 quarter phase changes.
 */
 
 #include <stdio.h>

demo/c/positions.c

@@ -1,7 +1,56 @@
+/*
+    positions.c  -  by Don Cross - 2019-06-11
+
+    Example C program for Astronomy Engine:
+    https://cosinekitty.github.io/astronomy/
+
+    Given an observer's geographic latitude and longitude,
+    and an optional date and time, this program displays the 
+    equatorial and horizontal coordinates of the Sun, Moon, and planets.
+    If the date and time is omitted from the command line, the
+    program uses the computer's current date and time.
+*/
+
 #include <stdio.h>
 #include "astronomy.h"
+#include "astro_demo_common.h"
 
 int main(int argc, const char *argv[])
 {
+    int error;
+    astro_observer_t observer;
+    astro_time_t time;
+    astro_body_t body;
+    astro_equatorial_t equ_2000, equ_ofdate;
+    astro_horizon_t hor;
+
+    error = ParseArgs(argc, argv, &observer, &time);
+    if (error)
+        return error;
+
+    printf("body        RA    DEC azimuth altitude\n");
+    for (body = MIN_BODY; body <= MAX_BODY; ++body)
+    {
+        if (body != BODY_EARTH)
+        {
+            equ_2000 = Astronomy_Equator(body, time, observer, EQUATOR_J2000, ABERRATION);
+            if (equ_2000.status != ASTRO_SUCCESS)
+            {
+                fprintf(stderr, "ERROR: Astronomy_Equator returned status %d trying to get J2000 coordinates.\n", equ_2000.status);
+                return 1;
+            }
+
+            equ_ofdate = Astronomy_Equator(body, time, observer, EQUATOR_OF_DATE, ABERRATION);
+            if (equ_ofdate.status != ASTRO_SUCCESS)
+            {
+                fprintf(stderr, "ERROR: Astronomy_Equator returned status %d trying to get coordinates of date.\n", equ_ofdate.status);
+                return 1;
+            }
+
+            hor = Astronomy_Horizon(time, observer, equ_ofdate.ra, equ_ofdate.dec, REFRACTION_NORMAL);
+            printf("%-7s %6.2lf %6.2lf %7.2lf %8.2lf\n", Astronomy_BodyName(body), equ_2000.ra, equ_2000.dec, hor.azimuth, hor.altitude);
+        }
+    }
+
     return 0;
 }

source/c/astronomy.h

@@ -193,6 +193,9 @@ astro_body_t;
 #define MIN_BODY    BODY_MERCURY    /**< Minimum valid astro_body_t value; useful for iteration. */
 #define MAX_BODY    BODY_MOON       /**< Maximum valid astro_body_t value; useful for iteration. */
 
+#define MIN_YEAR    1700    /**< Minimum year value supported by Astronomy Engine. */
+#define MAX_YEAR    2200    /**< Maximum year value supported by Astronomy Engine. */
+
 /**
  * @brief The location of an observer on (or near) the surface of the Earth.
  *

windows/examples/positions/positions.vcxproj

@@ -75,6 +75,7 @@
       <Optimization>Disabled</Optimization>
       <SDLCheck>true</SDLCheck>
       <AdditionalIncludeDirectories>C:\don\github\astronomy\source\c;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <PreprocessorDefinitions>_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
@@ -83,6 +84,7 @@
       <Optimization>Disabled</Optimization>
       <SDLCheck>true</SDLCheck>
       <AdditionalIncludeDirectories>C:\don\github\astronomy\source\c;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <PreprocessorDefinitions>_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
@@ -93,6 +95,7 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <SDLCheck>true</SDLCheck>
       <AdditionalIncludeDirectories>C:\don\github\astronomy\source\c;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <PreprocessorDefinitions>_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
     <Link>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
@@ -107,6 +110,7 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <SDLCheck>true</SDLCheck>
       <AdditionalIncludeDirectories>C:\don\github\astronomy\source\c;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <PreprocessorDefinitions>_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
     <Link>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
@@ -114,7 +118,13 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClCompile Include="..\..\..\demo\c\astro_demo_common.c" />
     <ClCompile Include="..\..\..\demo\c\positions.c" />
+    <ClCompile Include="..\..\..\source\c\astronomy.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="..\..\..\demo\c\astro_demo_common.h" />
+    <ClInclude Include="..\..\..\source\c\astronomy.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">

windows/examples/positions/positions.vcxproj.filters

@@ -18,5 +18,19 @@
     <ClCompile Include="..\..\..\demo\c\positions.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\source\c\astronomy.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="..\..\..\demo\c\astro_demo_common.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="..\..\..\demo\c\astro_demo_common.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="..\..\..\source\c\astronomy.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>