Look ma, it's a generator!

generator.nim

iterator additionIterator(value: int): int {.closure.} =
  var total = 0
  while True:
    total += value
    yield total

var addIter = additionIterator # Creates a *copy* of the original iterator procedure
for i in 1..5:
  echo(addIter(i)) # The argument the iterator takes is updated each time we call it.