Basic stack inventory code

/// Add to stack
ds_stack_push(inv, other);      // "other" being the other object (the item) involved in the collision
other.x=32*ds_stack_size(inv)*32;   // X position on screen, not important otherwise
other.y=32;             // Y position on screen, not important otherwise

/// Remove from stack
if (!ds_stack_empty(inv)){
    n=ds_stack_pop(inv);
    with (n)
        instance_destroy();
}