BiTable[T] = object
  vals: seq[T]               ## indexed by LitId
  keys: seq[LitId]           ## indexed by hash(val)
  

LitId = distinct uint32

proc `$`(x: LitId): string {.borrow, ...raises: [], tags: [].}

proc `<=`(x, y: LitId): bool {.borrow, ...raises: [], tags: [].}

proc `<`(x, y: LitId): bool {.borrow, ...raises: [], tags: [].}

proc `==`(x, y: LitId): bool {.borrow, ...raises: [], tags: [].}

proc `[]`[T](t: BiTable[T]; LitId: LitId): lent T {.inline.}

proc `[]`[T](t: var BiTable[T]; LitId: LitId): var T {.inline.}

proc getKeyId[T](t: BiTable[T]; v: T): LitId

proc getOrIncl[T](t: var BiTable[T]; v: T): LitId

proc hash(x: LitId): Hash {.borrow, ...raises: [], tags: [].}

proc hash[T](t: BiTable[T]): Hash

proc hasLitId[T](t: BiTable[T]; x: LitId): bool

proc len[T](t: BiTable[T]): int

proc load[T](f: var RodFile; t: var BiTable[T])

proc store[T](f: var RodFile; t: BiTable[T])