// stack:    inserts and removes happen at the same end
// insfirst: stack's action happens at the end called "first", "head" or "front"
// allhead:  inserts and removes happen via the api-provided "first"/"head"/"front"

#define BOP_INSERT(lst, ui, iters, i) BFX_INSERT_FIRST(B_UserItem, lst, ui[i])
#define BOP_REMOVE(lst, ui, iters, i) BFX_REMOVE_FIRST(B_UserItem, lst)