From 0d05cb75ee3c3d85481fe87ea287c97a439fe47a Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Sat, 1 Mar 2025 15:11:35 -0500
Subject: temperature conversion functions

---
 Makefile           |  2 +-
 test.c             |  9 +++++++++
 test.h             |  9 +++++++++
 test_temperature.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 unit.c             | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 unit.h             | 14 ++++++++++++++
 6 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 test_temperature.c

diff --git a/Makefile b/Makefile
index c2a54c5..3aa9131 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ SRC = main.c microui.c renderer.c widget.c ui.c unit.c engine.c
 OBJ = ${SRC:.c=.o}
 HDR = microui.h renderer.h widget.h ui.h unit.h engine.h
 
-TEST_SRC = test.c test_angular_speed.c test_pressure.c test_volume.c test_volume_flow_rate.c test_fraction.c unit.c
+TEST_SRC = test.c test_angular_speed.c test_pressure.c test_temperature.c test_volume.c test_volume_flow_rate.c test_fraction.c unit.c
 TEST_OBJ = ${TEST_SRC:.c=.o}
 
 volute: ${OBJ}
diff --git a/test.c b/test.c
index 5421adf..48df56e 100644
--- a/test.c
+++ b/test.c
@@ -23,6 +23,15 @@ main(void) {
 	test_as_bar();
 	test_as_psi();
 
+	test_kelvin();
+	test_celsius();
+	test_fahrenheit();
+	test_rankine();
+	test_as_kelvin();
+	test_as_celsius();
+	test_as_fahrenheit();
+	test_as_rankine();
+
 	test_cubic_centimetre();
 	test_litre();
 	test_cubic_metre();
diff --git a/test.h b/test.h
index 150443c..4504b00 100644
--- a/test.h
+++ b/test.h
@@ -29,6 +29,15 @@ void test_as_kilopascal(void);
 void test_as_bar(void);
 void test_as_psi(void);
 
+void test_kelvin(void);
+void test_celsius(void);
+void test_fahrenheit(void);
+void test_rankine(void);
+void test_as_kelvin(void);
+void test_as_celsius(void);
+void test_as_fahrenheit(void);
+void test_as_rankine(void);
+
 void test_cubic_centimetre(void);
 void test_litre(void);
 void test_cubic_metre(void);
diff --git a/test_temperature.c b/test_temperature.c
new file mode 100644
index 0000000..e7a6e17
--- /dev/null
+++ b/test_temperature.c
@@ -0,0 +1,45 @@
+#include <assert.h>
+#include <stdio.h>
+
+#include "test.h"
+#include "unit.h"
+
+void
+test_kelvin(void) {
+	test(kelvin(123.456), 123.456);
+}
+
+void
+test_celsius(void) {
+	test(celsius(123.456), 396.606);
+}
+
+void
+test_fahrenheit(void) {
+	test(fahrenheit(123.456), 323.9588889);
+}
+
+void
+test_rankine(void) {
+	test(rankine(123.456), 68.5866667);
+}
+
+void
+test_as_kelvin(void) {
+	test(as_kelvin(kelvin(123.456)), 123.456);
+}
+
+void
+test_as_celsius(void) {
+	test(as_celsius(celsius(123.456)), 123.456);
+}
+
+void
+test_as_fahrenheit(void) {
+	test(as_fahrenheit(fahrenheit(123.456)), 123.456);
+}
+
+void
+test_as_rankine(void) {
+	test(as_rankine(rankine(123.456)), 123.456);
+}
diff --git a/unit.c b/unit.c
index de24dc3..d1e487d 100644
--- a/unit.c
+++ b/unit.c
@@ -18,6 +18,9 @@
 /* Seconds per minute. */
 #define SEC_PER_MIN 60.0
 
+/* Zero Celsius in Kelvin. */
+#define ZERO_C 273.15
+
 
 AngularSpeed
 rad_per_sec(double x) {
@@ -108,6 +111,50 @@ as_psi(Pressure x) {
 }
 
 
+Temperature
+kelvin(double x) {
+	return x;
+}
+
+Temperature
+celsius(double x) {
+	return x + ZERO_C;
+}
+
+Temperature
+fahrenheit(double x) {
+	double c;
+
+	c = (x - 32.0) * 5.0 / 9.0;
+	return c + ZERO_C;
+}
+
+Temperature
+rankine(double x) {
+	return x * 5.0 / 9.0;
+}
+
+double
+as_kelvin(Temperature t) {
+	return t;
+}
+
+double
+as_celsius(Temperature t) {
+	return t - ZERO_C;
+}
+
+double
+as_fahrenheit(Temperature t) {
+	return as_celsius(t) * 9.0 / 5.0 + 32.0;
+}
+
+double
+as_rankine(Temperature t) {
+	return t * 9.0 / 5.0;
+}
+
+
 Volume
 cubic_centimetre(double x) {
 	return x * 1e-6;
diff --git a/unit.h b/unit.h
index 5febcd1..4e22a35 100644
--- a/unit.h
+++ b/unit.h
@@ -34,6 +34,20 @@ double as_bar(Pressure x);
 double as_psi(Pressure x);
 
 
+typedef double Temperature;
+typedef Temperature (*TemperatureMaker)(double);
+typedef double (*TemperatureReader)(Temperature);
+
+Temperature kelvin(double x);
+Temperature celsius(double x);
+Temperature fahrenheit(double x);
+Temperature rankine(double x);
+double as_kelvin(Temperature t);
+double as_celsius(Temperature t);
+double as_fahrenheit(Temperature t);
+double as_rankine(Temperature t);
+
+
 typedef double Volume;
 typedef Volume (*VolumeMaker)(double);
 typedef double (*VolumeReader)(Volume);
-- 
cgit v1.2.3