4 files changed, 180 insertions, 0 deletions
diff --git a/src/stack.nim b/src/stack.nim
index 2c6826d..eeef5cd 100644
--- a/src/stack.nim
+++ b/src/stack.nim
@@ -58,12 +58,24 @@ func Swap*(s: var Stack) =
   s.Push(b)
 
 func Transfert*(toss: var Stack, soss: var Stack, n: int) =
+  ## Implements a value transfert between two stacks, intended for use with the '{'
+  ## (aka begin) and '}' (aka end) stackstack commands
   toss.height += n
+  if toss.height > toss.size:
+    toss.size += 32
+    toss.data.setlen(toss.size)
   for i in 1..min(soss.height, n):
     toss.data[toss.height-i] = soss.data[soss.height-i]
+  for i in min(soss.height, n)+1..n:
+    toss.data[toss.height-i] = 0
   soss.height -= n
   if soss.height < 0:
     soss.height = 0
 
+func Discard*(s: var Stack, n: int) =
+  s.height -= n
+  if s.height < 0:
+    s.height = 0
+
 func Next*(s: Stack): ref Stack =
   return s.next
diff --git a/src/stackStack.nim b/src/stackStack.nim
new file mode 100644
index 0000000..6d32c87
--- /dev/null
+++ b/src/stackStack.nim
@@ -0,0 +1,57 @@
+import stack
+
+type
+  StackStack* = object
+    height: int
+    head: ref Stack
+
+func NewStackStack*(): ref StackStack =
+  result = new(StackStack)
+  result.head = NewStack()
+  result.height = 1
+
+func Pop*(ss: StackStack): int =
+  return ss.head[].Pop()
+
+func Push*(ss: StackStack, v: int) =
+  ss.head[].Push(v)
+
+func PopVector*(ss: StackStack): (int, int) =
+  return ss.head[].PopVector()
+
+func PushVector*(ss: var StackStack, v: tuple[x, y: int]) =
+  ss.head[].PushVector(v)
+
+func Clear*(ss: var StackStack) =
+  ss.head[].Clear()
+
+func Begin*(ss: var StackStack, v: tuple[x, y: int]) =
+  inc ss.height
+  let soss = ss.head
+  let n = soss[].Pop()
+  ss.head = NewStack(size = abs(n), next = soss)
+  let toss = ss.head
+  if n > 0:
+    toss[].Transfert(soss[], n)
+  elif n < 0:
+    for i in 0 ..< -n:
+      soss[].Push(0)
+  soss[].PushVector(v)
+
+func End*(ss: var StackStack, v: var tuple[x, y: int]): bool =
+  ## Implements the '}' command behaviour which pops a stack from the stack stack
+  ## returns true if a reflect should happen
+  if ss.height == 1:
+    return true
+  let toss = ss.head
+  let soss = toss[].Next()
+  let n = toss[].Pop()
+  v.y = soss[].Pop()
+  v.x = soss[].Pop()
+  if n > 0:
+    soss[].Transfert(toss[], n)
+  else:
+    soss[].Discard(-n)
+  dec ss.height
+  ss.head = soss
+  return false
diff --git a/tests/stack.nim b/tests/stack.nim
index 0f7e4c8..cb49daf 100644
--- a/tests/stack.nim
+++ b/tests/stack.nim
@@ -130,6 +130,13 @@ suite "Stack":
     check full.data[0] == 1
     check empty.data[0] == 2
     check empty.data[1] == 3
+  test "Discard":
+    var empty = NewStack()
+    empty[].Discard(1)
+    check empty.height == 0
+    empty[].Push(2)
+    empty[].Discard(3)
+    check empty.height == 0
   test "Next":
     var empty = NewStack()
     check empty[].Next() == nil
diff --git a/tests/stackStack.nim b/tests/stackStack.nim
new file mode 100644
index 0000000..03650f8
--- /dev/null
+++ b/tests/stackStack.nim
@@ -0,0 +1,104 @@
+import unittest
+
+include ../src/stackStack
+
+suite "StackStack":
+  test "Pop":
+    var empty = NewStackStack()
+    check empty[].Pop() == 0
+  test "Push":
+    var empty = NewStackStack()
+    empty[].Push(5)
+    check empty[].Pop() == 5
+  test "PopVector":
+    var empty = NewStackStack()
+    check empty[].PopVector() == (0, 0)
+  test "PushVector":
+    var empty = NewStackStack()
+    empty[].PushVector((3, 2))
+    check empty[].PopVector() == (3, 2)
+  test "Clear":
+    var empty = NewStackStack()
+    empty[].Push(3)
+    empty[].Clear()
+    check empty[].Pop() == 0
+  test "Begin":
+    var empty = NewStackStack()
+    empty[].Begin((1, 2))
+    check empty.height == 2
+    check empty[].Pop() == 0
+    empty[].Push(5)
+    empty[].Push(6)
+    empty[].Push(4)
+    empty[].Begin((3, 4))
+    check empty.height == 3
+    check empty[].Pop() == 6
+    check empty[].Pop() == 5
+    check empty[].Pop() == 0
+    check empty[].Pop() == 0
+    empty[].Push(7)
+    empty[].Push(8)
+    empty[].Push(9)
+    empty[].Push(2)
+    empty[].Begin((10, 11))
+    check empty.height == 4
+    check empty[].Pop() == 9
+    check empty[].Pop() == 8
+    check empty[].Pop() == 0
+    empty[].Push(13)
+    empty[].Push(14)
+    empty[].Push(-2)
+    empty[].Begin((15, 16))
+    check empty[].Pop() == 0
+  test "End":
+    var empty = NewStackStack()
+    var v: tuple[x,y: int] = (0, 0)
+    empty[].Push(1)
+    check empty[].End(v) == true
+    check empty.height == 1
+    check empty[].Pop() == 1
+    empty[].Push(1)
+    empty[].Push(2)
+    empty[].Push(3)
+    empty[].Push(4)
+    empty[].Push(2)
+    v = (5, 6)
+    empty[].Begin(v)
+    v = (0, 0)
+    empty[].Push(2)
+    check empty[].End(v) == false
+    check v == (5, 6)
+    check empty.height == 1
+    check empty[].End(v) == true
+    check empty[].Pop() == 4
+    check empty[].Pop() == 3
+    check empty[].Pop() == 2
+    check empty[].Pop() == 1
+    empty[].Push(1)
+    empty[].Push(2)
+    empty[].Push(3)
+    empty[].Push(4)
+    empty[].Push(2)
+    empty[].Begin(v)
+    empty[].Push(4)
+    check empty[].End(v) == false
+    check v == (5, 6)
+    check empty.height == 1
+    check empty[].Pop() == 4
+    check empty[].Pop() == 3
+    check empty[].Pop() == 0
+    check empty[].Pop() == 0
+    check empty[].Pop() == 2
+    check empty[].Pop() == 1
+    empty[].Push(1)
+    empty[].Push(2)
+    empty[].Push(3)
+    empty[].Push(4)
+    empty[].Push(1)
+    empty[].Begin(v)
+    empty[].Push(-2)
+    check empty[].End(v) == false
+    check v == (5, 6)
+    check empty.height == 1
+    check empty[].Pop() == 1
+    check empty[].Pop() == 0