# Pastebin aB77rjui
import options

proc mBind[T](o: Option[T], f: proc (value: T): T): Option[T] =
  if o.isSome:
    some f(o.get())
  else:
    none T

proc addOne(x: int): int = x + 1

let
  firstMaybe = some 1
  afterBind = firstMaybe.mBind(addOne)

assert afterBind.get == 2

let
  nothingMaybe = none int
  nothingAfterBind = nothingMaybe.mBind(addOne)

assert nothingAfterBind == none int