Array slicing in C

Question

In Python, if I wanted to assign the vector x=(1,2) to the first two elements of y=(0,0,0,0), I would do something like y[:1] = x. Is there an equivalent in C to assign a double x[2]={1.,2.} to the first two elements of an available double y[4] = {0.,0.,0.,0.}? Or will I have to loop?

Answer 1

Just try this

#include <string.h>
#include <stdio.h>

int main()
{
    double x[2] = {1., 2.};
    double y[4] = {0., 0., 0., 0.};

    memcpy(y, x, 2 * sizeof(*x));
              /* ^ 2 elements of size -> sizeof(double) */

    return 0;
}

instead of writing sizeof(double) which is ok, i did sizeof(*x) because if I change the type of x I wouldn't need to fix the memcpy, but i would also have to change the type of y in that case.