Generics in C

generics.c

/* See http://stackoverflow.com/a/16523865 */

#include <stdio.h>
#include "sum.h"

define_sum(int);
define_sum(double);


int main(void)
{
	double array1[] = {0.5, 1.5, 4.0};
	int array2[] = {1,2,3,4};

	printf("Double sum was %0.2G\n", sum(double)(array1, 3));
	printf("Integer sum was %d\n", sum(int)(array2, 4));

	return 0;
}

sum.h

#define sum(T) sum_##T

#define define_sum(T) \
	T sum_##T(T *values, size_t n) { \
		T sum = 0; \
		size_t i = 0; \
		for (i = 0; i < n; ++i) { \
			sum += values[i]; \
		} \
		return sum; \
	}