Simplify

Signed-off-by: Mattias Andrée <maandree@kth.se>

18 files changed, 417 insertions, 567 deletions

diff --git a/.gitignore b/.gitignore
index 8d3146b..b37ee8a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,8 @@
 *~
 *.o
 *.a
+*.i
 *.su
 *.so
 *.lo
+/generate-table
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..2a747f0
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,53 @@
+.POSIX:
+
+CONFIGFILE = config.mk
+include $(CONFIGFILE)
+
+all: libred.a
+solar.o: solar.c libred.h
+blackbody.o: blackbody.c 10deg-xy.i 10deg-rgb.i libred.h
+
+10deg-xy.i: 10deg
+	sed -e 's/^/{/' -e 's/ /, /' -e 's/$$/},/' < 10deg | sed '$$s/,$$//' > $@
+
+generate-table: generate-table.c blackbody.c 10deg-xy.i libred.h
+	$(CC) -o $@ generate-table.c $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
+
+10deg-rgb.i: generate-table 10deg
+	./generate-table > $@
+
+.c.o:
+	$(CC) -c -o $@ $< $(CPPFLAGS) $(CFLAGS)
+
+libred.a: solar.o blackbody.o
+	$(AR) rc $@ $?
+	$(AR) s $@
+
+install: libred.a
+	mkdir -p -- "$(DESTDIR)$(PREFIX)/lib"
+	mkdir -p -- "$(DESTDIR)$(PREFIX)/include"
+	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man0"
+	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man3"
+	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man7"
+	cp -- libred.a "$(DESTDIR)$(PREFIX)/lib"
+	cp -- libred.h "$(DESTDIR)$(PREFIX)/include"
+	cp -- libred.h.0 "$(DESTDIR)$(MANPREFIX)/man0"
+	cp -- libred_check_timetravel.3 libred_get_colour.3 libred_solar_elevation.3 "$(DESTDIR)$(MANPREFIX)/man3"
+	cp -- libred.7 "$(DESTDIR)$(MANPREFIX)/man7"
+
+uninstall:
+	-rm -f -- "$(DESTDIR)$(PREFIX)/lib/libred.a"
+	-rm -f -- "$(DESTDIR)$(PREFIX)/include/libred.h"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man0/libred.h.0"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man3/libred_check_timetravel.3"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man3/libred_get_colour.3"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man3/libred_solar_elevation.3"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man7/libred.7"
+
+clean:
+	-rm -f -- generate-table *.i *.o *.a *.lo *.su *.so
+
+.SUFFIXES:
+.SUFFIXES: .c .o
+
+.PHONY: all check install uninstall clean
diff --git a/blackbody.c b/blackbody.c
index 104e7da..9dfe1a8 100644
--- a/blackbody.c
+++ b/blackbody.c
@@ -4,173 +4,143 @@
 # pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
 #endif
 
-
 #ifndef LIBRED_COMPILING_PARSER
 #include "libred.h"
-#include "macros.h"
-#include <math.h>
 #include <errno.h>
-#include <fcntl.h>
-
-
-
-/**
- * The file descriptor to the colour lookup table.
- */
-int libred_fd = -1;
-
+#include <math.h>
+#include <stddef.h>
 
 
-/**
- * This function must be called, once,
- * before calling `libred_get_colour`.
- * 
- * @return  0 on success, -1 on error.
- * 
- * @throws  Any error specified for `open(3)`.
- */
-int
-libred_init_colour(void)
-{
-	libred_term_colour();
-	libred_fd = open(SYSDEPRESDIR "/" PACKAGE "/10deg", O_RDONLY);
-	return libred_fd < 0 ? -1 : 0;
-}
+struct xy {double x, y;};
+struct rgb {double r, g, b;};
 
+static struct xy xy_table[] = {
+#include "10deg-xy.i"
+};
 
-/**
- * Call this when the process will not
- * longer make calls to `libred_get_colour`.
- */
-void
-libred_term_colour(void)
-{
-	if (libred_fd >= 0)
-		close(libred_fd), libred_fd = -1;
-}
+static struct rgb rgb_table[] = {
+#include "10deg-rgb.i"
+};
 
 
 #endif
 /**
- * Convert from CIE xyY to [0, 1] sRGB.
+ * Convert from CIE xyY to [0, 1] sRGB
  * 
- * @param  x  The 'x' component.
- * @param  y  The 'y' component.
- * @param  Y  The 'Y' component.
- * @param  r  Output parameter for the “red” value.
- *            (Seriously, sRGB red is orange, just look at it fullscreen.)
- * @param  g  Output parameter for the green value.
- * @param  b  Output parameter for the blue value.
+ * @param  x  The 'x' component
+ * @param  y  The 'y' component
+ * @param  Y  The 'Y' component
+ * @param  r  Output parameter for the “red” value
+ *            (Seriously, sRGB red is orange, just look at it fullscreen)
+ * @param  g  Output parameter for the green value
+ * @param  b  Output parameter for the blue value
  */
 static void
 ciexyy_to_srgb(double x, double y, double Y, double *r, double *g, double *b)
 {
 #define SRGB(C)  (((C) <= 0.0031308) ? (12.92 * (C)) : ((1.0 + 0.055) * pow((C), 1.0 / 2.4) - 0.055))
-	double X, Z;
+	double X, Z, max;
   
 #if __GNUC__
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Wfloat-equal"
 #endif
-	/* Convert CIE xyY to CIE XYZ. */
+	/* Convert CIE xyY to CIE XYZ */
 	X = Y * (y == 0.0 ? 0.0 : (x / y));
 	Z = Y * (y == 0.0 ? 0.0 : ((1.0 - x - y) / y));
 #if __GNUC__
 # pragma GCC diagnostic pop
 #endif
   
-	/* Convert CIE XYZ to [0, 1] linear RGB. (ciexyz_to_linear) */
+	/* Convert CIE XYZ to [0, 1] linear RGB (ciexyz_to_linear) */
 	*r = ( 3.240450 * X) + (-1.537140 * Y) + (-0.4985320 * Z);
 	*g = (-0.969266 * X) + ( 1.876010 * Y) + ( 0.0415561 * Z);
 	*b = (0.0556434 * X) + (-0.204026 * Y) + ( 1.0572300 * Z);
   
-	/* Convert [0, 1] linear RGB to [0, 1] sRGB. */
+	/* Convert [0, 1] linear RGB to [0, 1] sRGB */
 	SRGB(*r), SRGB(*g), SRGB(*b);
+
+	/* Adjust colours for use */
+	max = fmax(fmax(fabs(*r), fabs(*g)), fabs(*b));
+#if __GNUC__
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wfloat-equal"
+#endif
+	if (max != 0.0)  *r /= max, *g /= max, *b /= max;
+#if __GNUC__
+# pragma GCC diagnostic pop
+#endif
+	*r = *r > 0.0 ? *r : 0.0;
+	*g = *g > 0.0 ? *g : 0.0;
+	*b = *b > 0.0 ? *b : 0.0;
 }
 #ifndef LIBRED_COMPILING_PARSER
 
-
 /**
  * Perform linear interpolation (considered very good)
  * between the CIE xyY values for two colour temperatures
  * and convert the result to sRGB. The two colours should
  * be the closest below the desired colour temperature,
- * and the closest above the desired colour temperature.
+ * and the closest above the desired colour temperature
  * 
- * @param  x1    The 'x' component for the low colour.
- * @param  y1    The 'y' component for the low colour.
- * @param  x2    The 'x' component for the high colour.
- * @param  y2    The 'y' component for the high colour.
- * @param  temp  The desired colour temperature.
- * @param  r     Output parameter for the “red” value.
- * @param  g     Output parameter for the green value.
- * @param  b     Output parameter for the blue value.
+ * @param  x1    The 'x' component for the low colour
+ * @param  y1    The 'y' component for the low colour
+ * @param  x2    The 'x' component for the high colour
+ * @param  y2    The 'y' component for the high colour
+ * @param  temp  The desired colour temperature
+ * @param  r     Output parameter for the “red” value
+ * @param  g     Output parameter for the green value
+ * @param  b     Output parameter for the blue value
  */
 static void
 interpolate(double x1, double y1, double x2, double y2, double temp, double *r, double *g, double *b)
 {
-	double weight = fmod(temp, (double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE;
+	double weight = fmod(temp - (LIBRED_LOWEST_TEMPERATURE % LIBRED_DELTA_TEMPERATURE),
+	                     (double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE;
 	double x = x1 * (1 - weight) + x2 * weight;
 	double y = y1 * (1 - weight) + y2 * weight;
 	ciexyy_to_srgb(x, y, 1.0, r, g, b);
 }
 
-
 /**
- * Get the [0, 1] sRGB values of a colour temperature.
- * 
- * @param   temp  The desired colour temperature.
- * @param   r     Output parameter for the “red” value.
- * @param   g     Output parameter for the green value.
- * @param   b     Output parameter for the blue value.
- * @return        0 on succeess, -1 on error.
+ * Get the [0, 1] sRGB values of a colour temperature
  * 
- * @throws  EOVERFLOW  The file did not have the expected size.
- * @throws  EDOM       The selected temperature is below 1000 K.
- * @throws             Any error specified for pread(3).
+ * @param   temp  The desired colour temperature
+ * @param   r     Output parameter for the “red” value
+ * @param   g     Output parameter for the green value
+ * @param   b     Output parameter for the blue value
+ * @return        0 on succeess, -1 on error
+ * @throws  EDOM  The selected temperature is below 1000 K
  */
 int
 libred_get_colour(long int temp, double *r, double *g, double *b)
 {
-	double values[10]; /* low:x,y,r,g,b + high:x,y,r,g,b */
-	off_t offset;
-	double max;
-
-	/* We do not have any values for above 40 000 K, but
-	 * the differences will be unnoticeable, perhaps even
-	 * unencodeable. */
-	if (temp > LIBRED_HIGHEST_TEMPERATURE)  temp = LIBRED_HIGHEST_TEMPERATURE;
-	/* Things do not glow below 1000 K. Yes, fire is hot! */
-	if (temp < LIBRED_LOWEST_TEMPERATURE)   t ((errno = EDOM));
-
-	/* Read table. */
-	offset = ((off_t)temp - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE;
-	offset *= (off_t)(sizeof(values) / 2);
-	errno = EOVERFLOW; xpread(libred_fd, values, sizeof(values), offset);
-
-	/* Get colour. */
-	if (temp % LIBRED_DELTA_TEMPERATURE)
-		interpolate(values[0], values[1], values[6], values[7], (double)temp, r, g, b);
-	else
-		*r = values[2], *g = values[3], *b = values[4];
-
-	/* Adjust colours for use. */
-	max = fmax(fmax(fabs(*r), fabs(*g)), fabs(*b));
-#if __GNUC__
-# pragma GCC diagnostic push
-# pragma GCC diagnostic ignored "-Wfloat-equal"
-#endif
-	if (max != 0.0)  *r /= max, *g /= max, *b /= max;
-#if __GNUC__
-# pragma GCC diagnostic pop
-#endif
-	*r = *r > 0.0 ? *r : 0.0;
-	*g = *g > 0.0 ? *g : 0.0;
-	*b = *b > 0.0 ? *b : 0.0;
+	double x1, y1, x2, y2;
+	size_t i;
+
+	if (temp > LIBRED_HIGHEST_TEMPERATURE)
+		temp = LIBRED_HIGHEST_TEMPERATURE;
+
+	if (temp < LIBRED_LOWEST_TEMPERATURE) {
+		errno = EDOM;
+		return -1;
+	}
+
+	if (temp % LIBRED_DELTA_TEMPERATURE) { /* TODO make optional */
+		i = (temp - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE;
+		x1 = xy_table[i].x;
+		y1 = xy_table[i].y;
+		x2 = xy_table[i + 1].x;
+		y2 = xy_table[i + 1].y;
+		interpolate(x1, y1, x2, y2, (double)temp, r, g, b);
+	} else {
+		i = (temp - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE;
+		*r = rgb_table[i].r;
+		*g = rgb_table[i].g;
+		*b = rgb_table[i].b;
+	}
 
 	return 0;
-fail:
-	return -1;
 }
 #endif
 
diff --git a/config.mk b/config.mk
new file mode 100644
index 0000000..32897e2
--- /dev/null
+++ b/config.mk
@@ -0,0 +1,6 @@
+PREFIX = /usr
+MANPREFIX = $(PREFIX)/share/man
+
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
+CFLAGS   = -std=c99 -Wall
+LDFLAGS  = -lm
diff --git a/generate-table.c b/generate-table.c
new file mode 100644
index 0000000..ac89af7
--- /dev/null
+++ b/generate-table.c
@@ -0,0 +1,43 @@
+/* See LICENSE file for copyright and license details. */
+#include "libred.h"
+#include <errno.h>
+#include <math.h>
+#include <string.h>
+#include <stdio.h>
+
+#if __GNUC__
+# pragma GCC diagnostic ignored "-Wfloat-equal"
+#endif
+
+struct xy {double x, y;};
+
+static struct xy xy_table[] = {
+#include "10deg-xy.i"
+};
+
+/* define ciexyy_to_srgb() and adjust_luma() */
+#define LIBRED_COMPILING_PARSER
+#include "blackbody.c"
+
+int
+main(void)
+{
+	long int temp = LIBRED_LOWEST_TEMPERATURE;
+	size_t i, n = sizeof(xy_table) / sizeof(*xy_table);
+	double r, g, b;
+
+	for (i = 0; i < n; i++, temp += LIBRED_DELTA_TEMPERATURE) {
+		if (temp == 6500)
+			r = g = b = 1;
+		else
+			ciexyy_to_srgb(xy_table[i].x, xy_table[i].y, 1, &r, &g, &b);
+		printf("{%a, %a, %a}%s\n", r, g, b, i + 1 == n ? "" : ",");
+	}
+
+	if (fflush(stdout) || ferror(stdout) || fclose(stdout)) {
+		perror(NULL);
+		return -1;
+	}
+
+	return 0;
+}
diff --git a/man/libred.7 b/libred.7
index a5a6f36..0e0b6b9 100644
--- a/man/libred.7
+++ b/libred.7
@@ -5,9 +5,7 @@ libred \- Solar elevation and blackbody colour calculation
 .B libred
 is a C library for calculating the Sun's apparent elevation
 and colours temperatures.
-.SH "FUTURE DIRECTIONS"
-None.
-.SH "SEE ALSO"
+.SH SEE ALSO
 .BR libred.h (0),
 .BR solar-python (7),
 .BR redshift (1),
diff --git a/libred.h b/libred.h
index 041a49e..57b17c7 100644
--- a/libred.h
+++ b/libred.h
@@ -5,216 +5,186 @@
 
 
 /**
- * Approximate apparent size of the Sun in degrees.
+ * Approximate apparent size of the Sun in degrees
  */
 #define LIBRED_SOLAR_APPARENT_RADIUS  (32.0 / 60.0)
 
 
 /**
- * The Sun's elevation at sunset and sunrise, measured in degrees.
+ * The Sun's elevation at sunset and sunrise, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_SUNSET_SUNRISE   (-32.0 / 60.0)
 
 /**
- * The Sun's elevation at civil dusk and civil dawn, measured in degrees.
+ * The Sun's elevation at civil dusk and civil dawn, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_CIVIL_DUSK_DAWN   (-6.0)
 
 /**
- * The Sun's elevation at nautical dusk and nautical dawn, measured in degrees.
+ * The Sun's elevation at nautical dusk and nautical dawn, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_NAUTICAL_DUSK_DAWN  (-12.0)
 
 /**
- * The Sun's elevation at astronomical dusk and astronomical dawn, measured in degrees.
+ * The Sun's elevation at astronomical dusk and astronomical dawn, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_ASTRONOMICAL_DUSK_DAWN  (-18.0)
 
 /**
- * The Sun's elevation at amateur astronomical dusk and amateur astronomical dawn, measured in degrees.
+ * The Sun's elevation at amateur astronomical dusk and amateur astronomical dawn, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_AMATEUR_ASTRONOMICAL_DUSK_DAWN  (-15.0)
 
 /**
- * The Sun's lowest elevation during the golden hour, measured in degrees.
+ * The Sun's lowest elevation during the golden hour, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_GOLDEN_HOUR_LOW  (-4.0)
 
 /**
- * The Sun's highest elevation during the golden hour, measured in degrees.
+ * The Sun's highest elevation during the golden hour, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_GOLDEN_HOUR_HIGH  (6.0)
 
 /**
- * The Sun's lowest elevation during the blue hour, measured in degrees.
+ * The Sun's lowest elevation during the blue hour, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_BLUE_HOUR_LOW  (-6.0)
 
 /**
- * The Sun's highest elevation during the blue hour, measured in degrees.
+ * The Sun's highest elevation during the blue hour, measured in degrees
  */
 #define LIBRED_SOLAR_ELEVATION_BLUE_HOUR_HIGH  (-4.0)
 
 
 /**
- * Test whether it is twilight.
+ * Test whether it is twilight
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is twilight, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is twilight, 0 otherwise
  */
 #define LIBRED_IS_TWILIGHT(ELEV)  ((-18.0 <= (ELEV)) && ((ELEV) <= -32.0 / 60.0))
 
 /**
- * Test whether it is civil twilight.
+ * Test whether it is civil twilight
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is civil twilight, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is civil twilight, 0 otherwise
  */
 #define LIBRED_IS_CIVIL_TWILIGHT(ELEV)  ((-6.0 <= (ELEV)) && ((ELEV) <= -32.0 / 60.0))
 
 /**
- * Test whether it is nautical twilight.
+ * Test whether it is nautical twilight
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is nautical twilight, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is nautical twilight, 0 otherwise
  */
 #define LIBRED_IS_NAUTICAL_TWILIGHT(ELEV)  ((-12.0 <= (ELEV)) && ((ELEV) <= -32.0 / 60.0))
 
 /**
- * Test whether it is astronomical twilight.
+ * Test whether it is astronomical twilight
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is astronomical twilight, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is astronomical twilight, 0 otherwise
  */
 #define LIBRED_IS_ASTRONOMICAL_TWILIGHT(ELEV)  ((-18.0 <= (ELEV)) && ((ELEV) <= -32.0 / 60.0))
 
 /**
- * Test whether it is amateur astronomical twilight.
+ * Test whether it is amateur astronomical twilight
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is amatuer astronomical twilight, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is amatuer astronomical twilight, 0 otherwise
  */
 #define LIBRED_IS_AMATEUR_ASTRONOMICAL_TWILIGHT(ELEV)  ((-18.0 <= (ELEV)) && ((ELEV) <= -15.0))
 
 /**
- * Test whether it is nighttime.
+ * Test whether it is nighttime
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is nighttime, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is nighttime, 0 otherwise
  */
 #define LIBRED_IS_NIGHTTIME(ELEV)  ((ELEV) < -18.0)
 
 /**
- * Test whether it is daytime.
+ * Test whether it is daytime
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is daytime, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is daytime, 0 otherwise
  */
 #define LIBRED_IS_DAYTIME(ELEV)  ((ELEV) > -32.0 / 60.0)
 
 /**
- * Test whether it is the golden hour.
+ * Test whether it is the golden hour
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is golden hour, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is golden hour, 0 otherwise
  */
 #define LIBRED_IS_GOLDEN_HOUR(ELEV)  ((-4.0 <= (ELEV)) && ((ELEV) <= 6.0))
 
 /**
- * Test whether it is the blue hour.
+ * Test whether it is the blue hour
  * 
- * @param   ELEV:double  The current elevation.
- * @return               1 if is blue hour, 0 otherwise.
+ * @param   ELEV:double  The current elevation
+ * @return               1 if is blue hour, 0 otherwise
  */
 #define LIBRED_IS_BLUE_HOUR(ELEV)  ((-6.0 <= (ELEV)) && ((ELEV) <= -4.0))
 
 
 /**
  * Calculates the Sun's elevation as apparent
- * from a geographical position.
+ * from a geographical position
  * 
  * @param   latitude   The latitude in degrees northwards from 
- *                     the equator, negative for southwards.
+ *                     the equator, negative for southwards
  * @param   longitude  The longitude in degrees eastwards from
- *                     Greenwich, negative for westwards.
- * @return             The Sun's apparent elevation as seen, right now,
- *                     from the specified position, measured in degrees.
- * 
- * @throws  0  On success.
- * @throws     Any error specified for clock_gettime(3) on error.
+ *                     Greenwich, negative for westwards
+ * @param   elevation  Output parameter for the Sun's apparent elevation
+ *                     as seen, right now, from the specified position,
+ *                     measured in degrees
+ * @return             0 on success, -1 on failure
+ * @throws             Any error specified for clock_gettime(3) on error
  */
-double libred_solar_elevation(double, double);
+double libred_solar_elevation(double, double, double *);
 
 
 /**
- * Exit if time the is before year 0 in J2000.
+ * Exit if time the is before year 0 in J2000
  * 
- * @return  0 on success, -1 on error.
+ * @return  0 on success, -1 on error
  */
 int libred_check_timetravel(void);
 
 
 
 /**
- * The highest colour temperature in the table.
+ * The highest colour temperature in the table
  */
 #define LIBRED_HIGHEST_TEMPERATURE  40000
 
 /**
- * The lowest colour temperature in the table.
+ * The lowest colour temperature in the table
  */
 #define LIBRED_LOWEST_TEMPERATURE  1000
 
 /**
  * The temperature difference between the colours in the table.
  * Note, `libred_get_colour` will make interpolation for colours
- * that are not in the table.
+ * that are not in the table
  */
 #define LIBRED_DELTA_TEMPERATURE  100
 
 
 /**
- * The file descriptor to the colour lookup table.
- * -1 if none is open.
- */
-extern int libred_fd;
-
-/**
- * Iff this macro is define `libred_fd` is available.
- */
-#define LIBRED_HAVE_FD  1
-
-
-/**
- * This function must be called, once,
- * before calling `libred_get_colour`.
- * 
- * @return  0 on success, -1 on error.
- * 
- * @throws  Any error specified for `open(3)`.
- */
-int libred_init_colour(void);
-
-/**
- * Call this when the process will not
- * longer make calls to `libred_get_colour`.
- */
-void libred_term_colour(void);
-
-/**
- * Get the [0, 1] sRGB values of a colour temperature.
+ * Get the [0, 1] sRGB values of a colour temperature
  * 
- * @param   temp  The desired colour temperature.
- * @param   r     Output parameter for the “red” value.
- * @param   g     Output parameter for the green value.
- * @param   b     Output parameter for the blue value.
- * @return        0 on succeess, -1 on error.
+ * @param   temp  The desired colour temperature
+ * @param   r     Output parameter for the “red” value
+ * @param   g     Output parameter for the green value
+ * @param   b     Output parameter for the blue value
+ * @return        0 on succeess, -1 on error
  * 
- * @throws  EOVERFLOW  The file did not have the expected size.
- * @throws  EDOM       The selected temperature is below 1000 K.
- * @throws             Any error specified for pread(3).
+ * @throws  EDOM  The selected temperature is below 1000 K
  */
-int libred_get_colour(long int, double*, double*, double*);
+int libred_get_colour(long int, double *, double *, double *);
 
 
 
diff --git a/man/libred.h.0 b/libred.h.0
index 95a5144..c3aa853 100644
--- a/man/libred.h.0
+++ b/libred.h.0
@@ -122,31 +122,9 @@ This header defines the following functions:
 .BR libred_check_timetravel (3)
 .TP
 *
-.BR libred_init_colour (3)
-.TP
-*
-.BR libred_term_colour (3)
-.TP
-*
 .BR libred_get_colour (3)
-.PP
-This header may define
-.B extern int libred_fd
-iff it does it also defines the macro
-.BR LIBRED_HAVE_FD .
-If it does, you want to keep this file descriptor open when you daemonise
-your process. It is set by
-.BR libred_init_colour (3)
-and unset by
-.BR libred_term_colour (3).
-It value is negative (more precisely it is -1) if no file descriptor has
-been opened.
-.SH "FUTURE DIRECTIONS"
-None.
-.SH "SEE ALSO"
+.SH SEE ALSO
 .BR libred (7),
 .BR libred_solar_elevation (3),
 .BR libred_check_timetravel (3),
-.BR libred_init_colour (3),
-.BR libred_term_colour (3),
 .BR libred_get_colour (3)
diff --git a/man/libred_check_timetravel.3 b/libred_check_timetravel.3
index 1d34d39..cf79cd2 100644
--- a/man/libred_check_timetravel.3
+++ b/libred_check_timetravel.3
@@ -11,8 +11,9 @@ int \fBlibred_check_timetravel\fP(void);
 Link with
 .IR -lred .
 .SH DESCRIPTION
-.B libred_check_timetravel
-exits the process if
+The
+.BR libred_check_timetravel ()
+function exits the process if
 .B libred
 is not compiled to support the current time, which is the case
 if it was compiled without
@@ -20,19 +21,16 @@ if it was compiled without
 and the clock is before year 2000.5 in the Julian calendar. Before
 exiting, the function will print an informative error message to
 standard error.
-.SH "RETURN VALUE"
+.SH RETURN VALUE
 Upon successful completion, without time incompatibility, the function
-returns 0. Upon failure, that is, it is unable to read the clock, the
-function returns -1.
+.BR libred_check_timetravel ()
+returns 0. On failure, the function returns -1 and sets
+.I errno
+to indicate the error.
 .SH ERRORS
 The function may fail for any reason specified for
-.BR clock_gettime (3),
-and set the value of
-.B errno
-to the same values.
-.SH "FUTURE DIRECTIONS"
-None.
-.SH "SEE ALSO"
+.BR clock_gettime (3).
+.SH SEE ALSO
 .BR libred.h (0),
 .BR libred (7),
 .BR libred_solar_elevation (3)
diff --git a/libred_get_colour.3 b/libred_get_colour.3
new file mode 100644
index 0000000..d169a60
--- /dev/null
+++ b/libred_get_colour.3
@@ -0,0 +1,54 @@
+.TH LIBRED_GET_COLOUR 3 LIBRED
+.SH NAME
+libred_get_colour \- Calculate a colour temperature
+.SH SYNOPSIS
+.nf
+#include <libred.h>
+
+int \fBlibred_get_colour\fP(long int \fItemp\fP, double *\fIr\fP, double *\fIg\fP, double *\fIb\fP);
+.fi
+.PP
+Link with
+.IR -lred .
+.SH DESCRIPTION
+.BR libred_get_colour ()
+gets or interpolates the colour temperature for
+.I temp
+kelvins, and returns the colour temperature in sRGB. The values,
+between 0.0 and 1.0, for the \(dqred\(dq, green, and blue channels
+are stored in
+.IR *r ,
+.IR *g ,
+and
+.IR *b ,
+respectively.
+.PP
+At least one of the values will be 1.0, none will be greater than
+1.0, and none will be less than 0.0. It is guaranteed (unless the
+resources file has been modified) that
+.IR *r ,
+.IR *g ,
+and
+.I *b
+all will be 1.0 if
+.I temp
+is 6500.
+.SH RETURN VALUE
+Upon successful completion, the
+.BR libred_get_colour ()
+function returns 0. On failure, the function returns -1 and sets
+.I errno
+to indicate the error.
+.SH ERRORS
+The function may fail if:
+.TP
+.B EDOM
+If
+.I temp
+is less than
+.B LIBRED_LOWEST_TEMPERATURE
+(which is 1000).
+.SH SEE ALSO
+.BR libred.h (0),
+.BR libred (7),
+.BR libred_get_solar_elevation (3)
diff --git a/libred_solar_elevation.3 b/libred_solar_elevation.3
new file mode 100644
index 0000000..9bb4b0a
--- /dev/null
+++ b/libred_solar_elevation.3
@@ -0,0 +1,40 @@
+.TH LIBRED_SOLAR_ELEVATION 3 LIBRED
+.SH NAME
+libred_solar_elevation \- Calculate the Sun's apparent elevation
+.SH SYNOPSIS
+.nf
+#include <libred.h>
+
+int \fBlibred_solar_elevation\fP(double \fIlatitude\fP, double \fIlongitude\fP, double *\felevation\fP);
+.fi
+.PP
+Link with
+.IR -lred .
+.SH DESCRIPTION
+.BR libred_solar_elevation ()
+calculates the Sun's elevation, and stores it, measured in degrees, in
+.IR *elevation ,
+as apparent from a selected geographical position, namely from
+.I latitude
+degrees north of GPS's equator and
+.I longitude
+degrees east of GPS's prime meridian. The function is only
+explicitly defined for values between -90 and +90 for
+.I latitude
+and values between -180 and +180 for and
+.IR longitude .
+Other values may or may not work, no error is thrown if used.
+.SH RETURN VALUE
+Upon successful completion, the 
+.BR libred_solar_elevation ()
+return 0, on failure it returns -1 and sets
+.I errno
+to indicate the error.
+.SH ERRORS
+The function may fail for any reason specified for
+.BR clock_gettime (3).
+.SH SEE ALSO
+.BR libred.h (0),
+.BR libred (7),
+.BR libred_check_timetravel (3),
+.BR libred_get_colour (3)
diff --git a/macros.h b/macros.h
deleted file mode 100644
index e760bd0..0000000
--- a/macros.h
+++ /dev/null
@@ -1,7 +0,0 @@
-/* See LICENSE file for copyright and license details. */
-#include <unistd.h>
-
-
-#define t(...)                      do { if   (__VA_ARGS__)  goto fail; } while (0)
-#define xpread(fd, buf, len, off)   t  (pread(fd, buf, len, off) < (ssize_t)(len))
-#define xwrite(fd, buf, len)        t  (write(fd, buf, len)      < (ssize_t)(len))
diff --git a/man/libred_get_colour.3 b/man/libred_get_colour.3
deleted file mode 100644
index fd32eb3..0000000
--- a/man/libred_get_colour.3
+++ /dev/null
@@ -1,74 +0,0 @@
-.TH LIBRED_GET_COLOUR 3 LIBRED
-.SH NAME
-libred_get_colour \- Calculate a colour temperature
-.SH SYNOPSIS
-.nf
-#include <libred.h>
-
-int \fBlibred_get_colour\fP(long int \fItemp\fP, double* \fIr\fP, double* \fIg\fP, double* \fIb\fP);
-.fi
-.PP
-Link with
-.IR -lred .
-.SH DESCRIPTION
-.B libred_get_colour
-gets or interpolates the colour temperature for
-.I temp
-kelvins, and returns the colour temperature in sRGB. The values,
-between 0.0 and 1.0, for the "red", green, and blue channels
-are stored in
-.IR *r ,
-.IR *g ,
-and
-.IR *b ,
-respectively.
-.PP
-At least one of the values will be 1.0, none will be greater than
-1.0, and none will be less than 0.0. It is guaranteed (unless the
-resources file has been modified) that
-.IR *r ,
-.IR *g ,
-and
-.I *b
-all will be 1.0 if
-.I temp
-is 6500.
-.PP
-You must call
-.BR libred_init_colour (3)
-before the first use of this function,
-and you should call
-.BR libred_term_colour (3)
-after the last use of this function.
-.SH "RETURN VALUE"
-Upon successful completion, the function returns 0. On failure,
-the function returns -1 and sets
-.B errno
-appropriately.
-.SH ERRORS
-The function may fail if:
-.TP
-.B EOVERFLOW
-The colour temperature lookup table is smaller than it should be.
-.TP
-.B EDOM
-If
-.I temp
-is less than
-.B LIBRED_LOWEST_TEMPERATURE
-(which is 1000.)
-.PP
-The function may also fail for any reason specified for
-.BR pread (3),
-and set the value of
-.B errno
-to the same values.
-.SH "FUTURE DIRECTIONS"
-It is possible that the behaviour is changed to loading the
-colour temperature lookup table rather than just open a
-file descriptor to it.
-.SH "SEE ALSO"
-.BR libred.h (0),
-.BR libred (7),
-.BR libred_init_colour (3),
-.BR libred_term_colour (3)
diff --git a/man/libred_init_colour.3 b/man/libred_init_colour.3
deleted file mode 100644
index 9463245..0000000
--- a/man/libred_init_colour.3
+++ /dev/null
@@ -1,41 +0,0 @@
-.TH LIBRED_INIT_COLOUR 3 LIBRED
-.SH NAME
-libred_init_colour \- Prepare for use of libred_get_colour(3)
-.SH SYNOPSIS
-.nf
-#include <libred.h>
-
-int \fBlibred_init_colour\fP(void);
-.fi
-.PP
-Link with
-.IR -lred .
-.SH DESCRIPTION
-.B libred_init_colour
-open a file descriptor, without returning it, to the colour
-temperature lookup table, and stores the file descriptor to
-.BR libred_fd .
-It is necessary to call this function before the first call to
-.BR libred_get_colour (3).
-.SH "RETURN VALUE"
-Upon successful completion, the function returns 0. On failure,
-the function returns -1 and sets
-.B errno
-appropriately.
-.SH ERRORS
-The function may fail for any reason specified for
-.BR open (3),
-and set the value of
-.B errno
-to the same values.
-.B errno
-is always set to 0 on success.
-.SH "FUTURE DIRECTIONS"
-It is possible that the behaviour is changed to loading the
-colour temperature lookup table rather than just open a
-file descriptor to it.
-.SH "SEE ALSO"
-.BR libred.h (0),
-.BR libred (7),
-.BR libred_get_colour (3),
-.BR libred_term_colour (3)
diff --git a/man/libred_solar_elevation.3 b/man/libred_solar_elevation.3
deleted file mode 100644
index 7fd499f..0000000
--- a/man/libred_solar_elevation.3
+++ /dev/null
@@ -1,48 +0,0 @@
-.TH LIBRED_SOLAR_ELEVATION 3 LIBRED
-.SH NAME
-libred_solar_elevation \- Calculate the Sun's apparent elevation
-.SH SYNOPSIS
-.nf
-#include <libred.h>
-
-double \fBlibred_solar_elevation\fP(double \fIlatitude\fP, double \fIlongitude\fP);
-.fi
-.PP
-Link with
-.IR -lred .
-.SH DESCRIPTION
-.B libred_solar_elevation
-calculates the Sun's  elevation as apparent from a select geographical position.
-Namely from
-.I latitude
-degrees north of GPS's equator and
-.I longitude
-degrees east of GPS's prime meridian. The function is only explicitly defined for
-values between -90 and +90 for
-.I latitude
-and values between -180 and +180 for and
-.IR longitude .
-Other values may or may not work, no error is thrown if used.
-.SH "RETURN VALUE"
-Upon successful completion, the function sets
-.B errno
-to 0 and returns the Sun's current apparent elevation, measured in
-degrees above the horizon. On failure, the function returns an
-arbitrary value (happens to always be 0.0) and sets
-.B errno
-an a non-zero value.
-.SH ERRORS
-The function may fail for any reason specified for
-.BR clock_gettime (3),
-and set the value of
-.B errno
-to the same values.
-.B errno
-is always set to 0 on success.
-.SH "FUTURE DIRECTIONS"
-None.
-.SH "SEE ALSO"
-.BR libred.h (0),
-.BR libred (7),
-.BR libred_check_timetravel (3),
-.BR libred_init_colour (3)
diff --git a/man/libred_term_colour.3 b/man/libred_term_colour.3
deleted file mode 100644
index 6d327c2..0000000
--- a/man/libred_term_colour.3
+++ /dev/null
@@ -1,33 +0,0 @@
-.TH LIBRED_TERM_COLOUR 3 LIBRED
-.SH NAME
-libred_term_colour \- Deallocate resources required by libred_get_colour(3)
-.SH SYNOPSIS
-.nf
-#include <libred.h>
-
-void \fBlibred_term_colour\fP(void);
-.fi
-.PP
-Link with
-.IR -lred .
-.SH DESCRIPTION
-.B libred_term_colour
-deallocates all resources acquired by
-.BR libred_init_colour (3).
-It is highly recommended to call this function before calling an
-.BR exec (3)-function.
-If you want to use
-.BR libred_get_colour (3)
-again after a call to this function has been made, you must first call
-.BR libred_init_colour (3).
-.SH "RETURN VALUE"
-None.
-.SH ERRORS
-None.
-.SH "FUTURE DIRECTIONS"
-None.
-.SH "SEE ALSO"
-.BR libred.h (0),
-.BR libred (7),
-.BR libred_get_colour (3),
-.BR libred_init_colour (3)
diff --git a/parse_10deg.c b/parse_10deg.c
deleted file mode 100644
index 4cdfd61..0000000
--- a/parse_10deg.c
+++ /dev/null
@@ -1,55 +0,0 @@
-/* See LICENSE file for copyright and license details. */
-#include "libred.h"
-#include "macros.h"
-#include <stdio.h>
-#include <math.h>
-#include <sys/stat.h>
-
-
-
-/**
- * The number of measured temperatures.
- */
-#define TEMPERATURES  ((LIBRED_HIGHEST_TEMPERATURE - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE + 1)
-
-
-
-#define LIBRED_COMPILING_PARSER
-#include "blackbody.c"
-
-
-
-/**
- * Create the lookup table of temperatures.
- * 
- * Standard input should be the file '10deg',
- * standard output should be the table file
- * and must be a regular file.
- * 
- * @param   argc  Should be 1.
- * @param   argv  Should only contain the name of the process.
- * @return        0 on success, 1 on error.
- */
-int
-main(int argc, char *argv[])
-{
-#define x  (xyrgb[0])
-#define y  (xyrgb[1])
-#define r  (xyrgb[2])
-#define g  (xyrgb[3])
-#define b  (xyrgb[4])
-  
-	double xyrgb[5];
-	struct stat attr;
-	long int temp = LIBRED_LOWEST_TEMPERATURE;
-  
-	for (; fscanf(stdin, "%lf %lf\n", &x, &y) == 2; temp += LIBRED_DELTA_TEMPERATURE) {
-		(temp == 6500) ? (r = g = b = 1.0) : ciexyy_to_srgb(x, y, 1.0, &r, &g, &b);
-		xwrite(STDOUT_FILENO, xyrgb, sizeof(xyrgb));
-	}
-	xwrite(STDOUT_FILENO, xyrgb, sizeof(xyrgb)); /* sugar */
-	t (fstat(STDOUT_FILENO, &attr));
-	return ((size_t)(attr.st_size) != (TEMPERATURES + 1) * 5 * sizeof(double));
-fail:
-	return perror(argc ? *argv : "parse_10deg"), 1;
-}
diff --git a/solar.c b/solar.c
index c2f67bc..906386f 100644
--- a/solar.c
+++ b/solar.c
@@ -11,8 +11,6 @@
 # pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
 #endif
 
-
-
 /* Select clock. */
 #if defined(DO_NOT_USE_COARSEC_CLOCK) || !defined(CLOCK_REALTIME_COARSE)
 # ifdef CLOCK_REALTIME_COARSE
@@ -21,30 +19,26 @@
 # define CLOCK_REALTIME_COARSE  CLOCK_REALTIME
 #endif
 
-
-
 /**
- * Get current Julian Centuries time (100 Julian days since J2000.)
- * 
- * @return  The current Julian Centuries time.
+ * Get current Julian Centuries time (100 Julian days since J2000)
  * 
- * @throws  0  On success.
- * @throws     Any error specified for clock_gettime(3) on error.
+ * @param   nowp  Output parameter for the current Julian Centuries time
+ * @return        0 on success, -1 on failure
+ * @throws        Any error specified for clock_gettime(3) on error
  */
 static double
-julian_centuries()
+julian_centuries(double *nowp)
 {
 	struct timespec now;
-	double tm;
 	if (clock_gettime(CLOCK_REALTIME_COARSE, &now))
-		return 0.0;
-	tm = (double)(now.tv_nsec) / 1000000000.0 + (double)(now.tv_sec);
-	tm = (tm / 86400.0 + 2440587.5 - 2451545.0) / 36525.0;
-	return errno = 0, tm;
+		return -1;
+	*nowp = (double)(now.tv_nsec) / 1000000000.0 + (double)(now.tv_sec);
+	*nowp = (*nowp / 86400.0 + 2440587.5 - 2451545.0) / 36525.0;
+	return 0;
 }
 
 /**
- * Convert a Julian Centuries timestamp to a Julian Day timestamp.
+ * Convert a Julian Centuries timestamp to a Julian Day timestamp
  * 
  * @param   tm  The time in Julian Centuries
  * @return      The time in Julian Days
@@ -57,7 +51,7 @@ julian_centuries_to_julian_day(double tm)
 
 
 /**
- * Convert an angle (or otherwise) from degrees to radians.
+ * Convert an angle (or otherwise) from degrees to radians
  * 
  * @param  deg  The angle in degrees.
  * @param       The angle in radians.
@@ -69,7 +63,7 @@ radians(double deg)
 }
 
 /**
- * Convert an angle (or otherwise) from radians to degrees.
+ * Convert an angle (or otherwise) from radians to degrees
  * 
  * @param  rad  The angle in radians.
  * @param       The angle in degrees.
@@ -84,11 +78,11 @@ degrees(double rad)
 /**
  * Calculates the Sun's elevation from the solar hour angle
  * 
- * @param   longitude    The longitude in degrees eastwards.
- *                       from Greenwich, negative for westwards.
- * @param   declination  The declination, in radians.
- * @param   hour_angle   The solar hour angle, in radians.
- * @return               The Sun's elevation, in radians.
+ * @param   longitude    The longitude in degrees eastwards
+ *                       from Greenwich, negative for westwards
+ * @param   declination  The declination, in radians
+ * @param   hour_angle   The solar hour angle, in radians
+ * @return               The Sun's elevation, in radians
  */
 static inline double
 elevation_from_hour_angle(double latitude, double declination, double hour_angle)
@@ -100,10 +94,10 @@ elevation_from_hour_angle(double latitude, double declination, double hour_angle
 }
 
 /**
- * Calculates the Sun's geometric mean longitude.
+ * Calculates the Sun's geometric mean longitude
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The Sun's geometric mean longitude in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The Sun's geometric mean longitude in radians
  */
 static inline double
 sun_geometric_mean_longitude(double tm)
@@ -116,10 +110,10 @@ sun_geometric_mean_longitude(double tm)
 }
 
 /**
- * Calculates the Sun's geometric mean anomaly.
+ * Calculates the Sun's geometric mean anomaly
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The Sun's geometric mean anomaly in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The Sun's geometric mean anomaly in radians
  */
 static inline double
 sun_geometric_mean_anomaly(double tm)
@@ -128,10 +122,10 @@ sun_geometric_mean_anomaly(double tm)
 }
 
 /**
- * Calculates the Earth's orbit eccentricity.
+ * Calculates the Earth's orbit eccentricity
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The Earth's orbit eccentricity.
+ * @param   tm  The time in Julian Centuries
+ * @return      The Earth's orbit eccentricity
  */
 static inline double
 earth_orbit_eccentricity(double tm)
@@ -141,10 +135,10 @@ earth_orbit_eccentricity(double tm)
 
 /**
  * Calculates the Sun's equation of the centre, the difference
- * between the true anomaly and the mean anomaly.
+ * between the true anomaly and the mean anomaly
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The Sun's equation of the centre, in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The Sun's equation of the centre, in radians
  */
 static inline double
 sun_equation_of_centre(double tm)
@@ -157,10 +151,10 @@ sun_equation_of_centre(double tm)
 }
 
 /**
- * Calculates the Sun's real longitudinal position.
+ * Calculates the Sun's real longitudinal position
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The longitude, in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The longitude, in radians
  */
 static inline double
 sun_real_longitude(double tm)
@@ -169,10 +163,10 @@ sun_real_longitude(double tm)
 }
 
 /**
- * Calculates the Sun's apparent longitudinal position.
+ * Calculates the Sun's apparent longitudinal position
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The longitude, in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The longitude, in radians
  */
 static inline double
 sun_apparent_longitude(double tm)
@@ -183,10 +177,10 @@ sun_apparent_longitude(double tm)
 
 /**
  * Calculates the mean ecliptic obliquity of the Sun's
- * apparent motion without variation correction.
+ * apparent motion without variation correction
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The uncorrected mean obliquity, in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The uncorrected mean obliquity, in radians
  */
 static double
 mean_ecliptic_obliquity(double tm)
@@ -197,10 +191,10 @@ mean_ecliptic_obliquity(double tm)
 
 /**
  * Calculates the mean ecliptic obliquity of the Sun's
- * parent motion with variation correction.
+ * parent motion with variation correction
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The mean obliquity, in radians.
+ * @param   tm  The time in Julian Centuries
+ * @return      The mean obliquity, in radians
  */
 static double
 corrected_mean_ecliptic_obliquity(double tm)
@@ -210,10 +204,10 @@ corrected_mean_ecliptic_obliquity(double tm)
 }
 
 /**
- * Calculates the Sun's declination.
+ * Calculates the Sun's declination
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The Sun's declination, in radian.
+ * @param   tm  The time in Julian Centuries
+ * @return      The Sun's declination, in radian
  */
 static inline double
 solar_declination(double tm)
@@ -224,10 +218,10 @@ solar_declination(double tm)
 
 /**
  * Calculates the equation of time, the discrepancy
- * between apparent and mean solar time.
+ * between apparent and mean solar time
  * 
- * @param   tm  The time in Julian Centuries.
- * @return      The equation of time, in degrees.
+ * @param   tm  The time in Julian Centuries
+ * @return      The equation of time, in degrees
  */
 static inline double
 equation_of_time(double tm)
@@ -245,15 +239,15 @@ equation_of_time(double tm)
 
 /**
  * Calculates the Sun's elevation as apparent
- * from a geographical position.
+ * from a geographical position
  * 
- * @param   tm         The time in Julian Centuries.
+ * @param   tm         The time in Julian Centuries
  * @param   latitude   The latitude in degrees northwards from 
- *                     the equator, negative for southwards.
+ *                     the equator, negative for southwards
  * @param   longitude  The longitude in degrees eastwards from
- *                     Greenwich, negative for westwards.
+ *                     Greenwich, negative for westwards
  * @return             The Sun's apparent elevation at the specified time as seen
- *                     from the specified position, measured in radians.
+ *                     from the specified position, measured in radians
  */
 static inline double
 solar_elevation_from_time(double tm, double latitude, double longitude)
@@ -265,35 +259,37 @@ solar_elevation_from_time(double tm, double latitude, double longitude)
 	return elevation_from_hour_angle(latitude, solar_declination(tm), rc);
 }
 
-
 /**
  * Calculates the Sun's elevation as apparent
- * from a geographical position.
+ * from a geographical position
  * 
  * @param   latitude   The latitude in degrees northwards from 
- *                     the equator, negative for southwards.
+ *                     the equator, negative for southwards
  * @param   longitude  The longitude in degrees eastwards from
- *                     Greenwich, negative for westwards.
- * @return             The Sun's apparent elevation as seen, right now,
- *                     from the specified position, measured in degrees.
- * 
- * @throws  0  On success.
- * @throws     Any error specified for clock_gettime(3) on error.
+ *                     Greenwich, negative for westwards
+ * @param   elevation  Output parameter for the Sun's apparent elevation
+ *                     as seen, right now, from the specified position,
+ *                     measured in degrees
+ * @return             0 on success, -1 on failure
+ * @throws             Any error specified for clock_gettime(3) on error
  */
 double
-libred_solar_elevation(double latitude, double longitude)
+libred_solar_elevation(double latitude, double longitude, double *elevation)
 {
-	double tm = julian_centuries();
-	return errno ? -1 : degrees(solar_elevation_from_time(tm, latitude, longitude));
+	double tm;
+	if (julian_centuries(&tm))
+		return -1;
+	*elevation = degrees(solar_elevation_from_time(tm, latitude, longitude));
+	return 0;
 }
 
-
 /**
- * Exit if time the is before year 0 in J2000.
+ * Exit if time the is before year 0 in J2000
  * 
- * @return  0 on success, -1 on error.
+ * @return  0 on success, -1 on error
  */
-int libred_check_timetravel(void)
+int
+libred_check_timetravel(void)
 {
 #if !defined(TIMETRAVELLER)
 	struct timespec now;