Casting one C structure into another

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.

Answer 2

You could use a pointer to do the typecast;

vector = *((Vector3d *) &acceleration);