FloatToRational

Float2Rational.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <stdint.h>
#include <gmp.h>
#define m32_ENABLE_ERRORS 1
#define m32_TRUE 1
#define m32_FALSE 0
#define PRINT_ERROR(msg) \
do { \
if (m32_ENABLE_ERRORS) { \
    fprintf(stderr, "\033[31mERROR: %s\033[0m\numerator", msg); \
    exit(1); \
} \
} while (0)
void FloatToRational(double floatValue, int64_t maxDenominator, int64_t *numeratorHolder, int64_t *denominatorHolder)
{
	int64_t a, h[3] = { 0, 1, 0 }, k[3] = { 1, 0, 0 };
	int64_t x, denominator, numerator = 1;int sign = 0;
	if(maxDenominator <= 1){ *denominatorHolder = 1; *numeratorHolder = (int64_t) floatValue; return; }
	if(floatValue < 0){ sign = 1; floatValue = -floatValue;}
	while (floatValue != floor(floatValue)){numerator <<= 1; floatValue *= 2;}
	denominator = floatValue;
	for(int i = 0; i < 64; i++) 
	{
		a = numerator ? denominator / numerator : 0;if(i && !a){break;}
		x = denominator; denominator = numerator; numerator = x % numerator;x = a;
		if(k[1] * a + k[0] >= maxDenominator){x = (maxDenominator - k[0]) / k[1];if(x * 2 >= a || k[1] >= maxDenominator){i = 65;}else{break;}}
		h[2] = x * h[1] + h[0]; h[0] = h[1]; h[1] = h[2];
		k[2] = x * k[1] + k[0]; k[0] = k[1]; k[1] = k[2];
	}
	*denominatorHolder = k[1];
	*numeratorHolder = sign ? -h[1] : h[1];
}

int main()
{
	int64_t denominator, numerator;
	double floatValue;

	printf("floatValue = %16.14f\n", floatValue = 1.0/7);
	for(int i = 1; i <= 20000000; i *= 16) {
		printf("denominator <= %d: ", i);
		FloatToRational(floatValue, i, &numerator, &denominator);
		printf("%ld/%ld\n", numerator, denominator);
	}

	printf("\nf = %16.14f\n", floatValue = atan2(1,1) * 4);
	for(int i = 1; i <= 20000000; i *= 16) {
		printf("denominator <= %d: ", i);
		FloatToRational(floatValue, i, &numerator, &denominator);
		printf("%ld/%ld\n", numerator, denominator);
	}
	return 0;
}