digression. apparently I needed to prove to myself that I could implement Celsius <-> Fahrenheit conversion in C. derp.

math-replay/.gitignore

@@ -2,3 +2,4 @@
 *.log
 *.pdf
 *.html
+temperatures

math-replay/Makefile

@@ -1,5 +1,8 @@
+CFLAGS += -g -Wall -Wextra
+
 ALL := $(patsubst %.haml,%.html,$(shell find . -name '*.haml'))
 ALL += $(patsubst %.tex,%.pdf,$(shell find . -name '*.tex'))
+ALL += temperatures
 
 
 %.html:%.haml

math-replay/temperatures.c

@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+double c2f(double celsius) {
+    return ((9.0 / 5.0) * celsius) + 32.0;
+}
+
+
+double f2c(double fahrenheit) {
+    return (5.0 / 9.0) * (fahrenheit - 32.0);
+}
+
+
+int die_usage(const char *msg) {
+    printf("Usage: temperatures [FC]<temp>\n");
+    printf("%s\n", msg);
+    exit(1);
+}
+
+
+int main(int argc, char * argv[]) {
+    if (argc < 2) {
+        die_usage("");
+    }
+
+    char msg[255];
+    double temp;
+    const char * temp_string = argv[1];
+
+    size_t temp_len = strlen(temp_string);
+
+    if (strncmp(temp_string, "F", temp_len) > -1) {
+        sscanf(temp_string, "F%lf", &temp);
+        printf("%.2lf\n", f2c(temp));
+    } else if (strncmp(temp_string, "C", temp_len) > -1) {
+        sscanf(temp_string, "C%lf", &temp);
+        printf("%.2lf\n", c2f(temp));
+    } else {
+        sprintf(msg, "Argument '%s' does not match '[FC]<temp>'",
+                temp_string);
+        die_usage(msg);
+    }
+
+    return 0;
+}