Source code in the nim programming language

iterator comb(m, n: int): seq[int] =
  var c = newSeq[int](n)
  for i in 0 ..< n: c[i] = i

  block outer:
    while true:
      yield c

      var i = n - 1
      inc c[i]
      if c[i] <= m - 1: continue

      while c[i] >= m - n + i:
        dec i
        if i < 0: break outer
      inc c[i]
      while i < n-1:
        c[i+1] = c[i] + 1
        inc i

for i in comb(5, 3):
  echo i


iterator combinations(m: int, n: int): seq[int] =

  var result = newSeq[int](n)
  var stack = newSeq[int]()
  stack.add 0

  while stack.len > 0:
    var index = stack.high
    var value = stack.pop()

    while value < m:
      result[index] = value
      inc value
      inc index
      stack.add value

      if index == n:
        yield result
        break
 
for i in combinations(5, 3):
  echo i