// queue:    inserts and removes happen at opposite ends
// inslast:  elements flow from "last", "tail" or "back", to "first," "head" or "front"
// inselem:  inserts happen via an element-level operation and removes happen via the api-provided "first"/"tail"/"front"

#define BOP_INIT(lst, iters, insNo, item)    BFX_INSERT_LAST(B_UserItem, lst, (item))

#define BOP_INSERT(lst, iters, insNo, item)  BFX_INSERT_AFTER(B_UserItem, lst, (item), iters[(insNo)-1])
#define BOP_REMOVE(lst, iters, remNo)        BFX_REMOVE_FIRST(B_UserItem, lst)