#include <stdio.h>

// matrix multiply float?
void matmulf(double *y , double A[][2], double *x)
{
	y[0] = A[0][0] * x[0] + A[0][1] * x[1];
	y[1] = A[1][0] * x[0] + A[1][1] * x[1];
}

int main()
{
	double A[][2] = {
		{1,0},
		{0,1},
	};
	double x[] = {10,20};
	double y[2];

	matmulf(y, A, x);
	printf("y=(%f,%f)\n", y[0], y[1]);
	return 0;
}