Pointers to Structs

Arrow vs dot

struct Point p = {1, 2};
struct Point *pp = &p;

p.x            // through the variable: dot
pp->x          // through the pointer: arrow
(*pp).x        // same thing, written the hard way

Walking an array of structs

struct Point pts[3] = {{1, 1}, {2, 4}, {3, 9}};
struct Point *end = pts + 3;
for (struct Point *it = pts; it < end; it++) {
    printf("(%d,%d)\n", it->x, it->y);   // it++ moves one WHOLE struct
}

Pointer arithmetic scales by sizeof(struct Point) — one step, one struct.

Mixed models

A common C API shape: the array is passed as a pointer, each element used through the arrow:

int total_x(struct Point *pts, int n) {
    int s = 0;
    for (int i = 0; i < n; i++) s += pts[i].x;   // or (pts+i)->x
    return s;
}

NULL discipline applies too

A struct pointer can be NULL; any function that receives one must either trust the contract or check it, just like int pointers.