c - Assigning values to pointers? -

in dennis ritchie found this,

struct rect r , *rp = r; 

then these 4 expressions equivalent :

1. r.pt1.x
2. rp->pt1.x
3. (r.pt1).x
4. (rp->pt1).x

because operators associate left right.
shouldn't struct rect *rp = &r?

absolutely -- address operator required, otherwise compile-time error:

incompatible types when initializing type ‘struct rect *’ using type ‘struct rect’