Question

I have two identical (but differently named) C structures:

typedef struct {
      double x;
      double y;
      double z;
} CMAcceleration;


typedef struct {
    double x;
    double y;
    double z;   
} Vector3d;

Now I want to assign a CMAcceleration variable to a Vector3d variable (copying the whole struct). How can I do this?

I tried the following but get these compiler errors:

vector = acceleration;           // "incompatible type"
vector = (Vector3d)acceleration; // "conversion to non-scalar type requested"

Of course I can resort to set all members individually:

vector.x = acceleration.x;
vector.y = acceleration.y;
vector.z = acceleration.z;

but that seems rather inconvenient.

What’s the best solution?

Answer 1

That’s your only solution (apart from wrapping it into a function):

vector.x = acceleration.x;
vector.y = acceleration.y;
vector.z = acceleration.z;

You could actually cast it, like this (using pointers)

Vector3d *vector = (Vector3d*) &acceleration;

but this is not in the specs and therefore the behaviour depends on the compiler, runtime and the big green space monster.