- Added error procedure.

src/error.c

@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <stdarg.h>
+#include "error.h"
+
+//! Print error message and die.
+/**
+ * Adapted from [K&R2], p. 174
+ * Input is comparable to printf, only end of line is not required.
+ */
+void error (char *fmt, ...)
+{
+  va_list args;
+
+  va_start (args, fmt);
+  fprintf (stderr, "error: ");
+  vprintf (stderr, fmt, args);
+  fprintf (stderr, "\n");
+  va_end (args);
+  exit(1);
+}

src/error.h

@@ -0,0 +1,6 @@
+#ifndef ERROR
+#define ERROR
+
+void error (char *fmt, ...)
+
+#endif