1 files changed, 71 insertions, 0 deletions
diff --git a/assorted/tofrac.c b/assorted/tofrac.c
new file mode 100644
index 0000000..e4c1480
--- /dev/null
+++ b/assorted/tofrac.c
@@ -0,0 +1,71 @@
+/*
+ *	libHX/assorted/tofrac.c
+ *	Copyright Jan Engelhardt, 1999-2010
+ *
+ *	This file is part of libHX. libHX is free software; you can
+ *	redistribute it and/or modify it under the terms of the GNU Lesser
+ *	General Public License as published by the Free Software Foundation;
+ *	either version 2.1 or (at your option) any later version.
+ */
+/*
+ *	Calculates a readable fraction (i.e. 1/3) from arg and puts the
+ *	*numerator into num, the denominator into *denom. Since the fraction
+ *	is found out by an iterative loop, you can specify the minimum value
+ *	of the denominator in *num and the maximum value of the denominator
+ *	into *denom before calling the function.
+ *
+ *	If a suitable fraction has been found (within the range of the
+ *	minimum / maximum denominator, *num and *denom will be overwritten
+ *	with the results and true is returned; false for no success.
+ *
+ *	You need to re-put your min/max denom values into *num and *denom
+ *	then.
+ */
+#include <sys/types.h>
+#include <limits.h>
+#include <math.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* This simplistic version does not deal with negative numbers. */
+
+static bool HX_tofrac(double arg, unsigned long *num, unsigned long *denom)
+{
+	unsigned long i, min_denom = *num, max_denom = *denom;
+	double j, s;
+
+	/*
+	 * This tries all possible denominators until @arg multiplied by @i
+	 * gives a number that has a fractional part of 0, which is when we
+	 * found the optimal fraction.
+	 */
+	for (i = min_denom; i < max_denom; ++i) {
+		s = arg * i;
+		modf(s, &j);
+		if (s == j) {
+			*num   = j;
+			*denom = i;
+			return true;
+		}
+	}
+	return false;
+}
+
+int main(int argc, const char **argv)
+{
+	unsigned long d = 1, n = ULONG_MAX;
+
+	if (argc < 2) {
+		fprintf(stderr, "Usage: %s 3.141592\n", *argv);
+		return EXIT_FAILURE;
+	}
+
+	if (!HX_tofrac(strtod(argv[1], NULL), &d, &n)) {
+		fprintf(stderr, "Our algorithm was too weak :-)\n");
+		return EXIT_FAILURE;
+	}
+
+	printf("%lu/%lu\n", d, n);
+	return EXIT_SUCCESS;
+}