Implemented the funge stack

src/stack.nim

@@ -0,0 +1,69 @@
+type
+  Stack* = object
+    size, height: int
+    data: seq[int]
+    next: ref Stack
+
+func NewStack*(size: int = 32, next: ref Stack = nil): ref Stack =
+  result = new(Stack)
+  result.size = size
+  result.data.setlen(size)
+  result.next = next
+
+func Pop*(s: var Stack): int =
+  if s.height > 0:
+    dec s.height
+    return s.data[s.height]
+  return 0
+
+func Push*(s: var Stack, v: int) =
+  if s.height >= s.size:
+    s.size += 32
+    s.data.setlen(s.size)
+  s.data[s.height] = v
+  inc s.height
+
+func PopVector*(s: var Stack): (int, int) =
+  if s.height >= 2:
+    s.height -= 2
+    return (s.data[s.height], s.data[s.height+1])
+  elif s.height == 1:
+    s.height = 0
+    return (0, s.data[0])
+  else:
+    return (0, 0)
+
+func PushVector*(s: var Stack, v: tuple[x, y: int]) =
+  if s.height+1 >= s.size:
+    s.size += 32
+    s.data.setlen(s.size)
+  s.data[s.height] = v.x
+  inc s.height
+  s.data[s.height] = v.y
+  inc s.height
+
+func Clear*(s: var Stack) =
+  s.height = 0
+
+func Duplicate*(s: var Stack) =
+  if s.height > 0:
+    s.Push(s.data[s.height-1])
+  else:
+    s.PushVector((0, 0))
+
+func Swap*(s: var Stack) =
+  let a = s.Pop
+  let b = s.Pop
+  s.Push(a)
+  s.Push(b)
+
+func Transfert*(toss: var Stack, soss: var Stack, n: int) =
+  toss.height += n
+  for i in 1..min(soss.height, n):
+    toss.data[toss.height-i] = soss.data[soss.height-i]
+  soss.height -= n
+  if soss.height < 0:
+    soss.height = 0
+
+func Next*(s: Stack): ref Stack =
+  return s.next