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/*
* 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;
}
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