||:@include: lib/rpn.nv

|:: push $x to $y|
    :stacks: $y $x
|:: pop from $x :stacks: $x $y|
    :item: $y
|:: pop from $x? :stacks: $y $z|
    :seen: $y $z
|:: pop from $x|
    :stack empty: $x
    :: reset stacks

|:: reset stacks? :seen: $x $y|
    :stacks: $x $y
|:: reset stacks|

|:: $x for all $y :stack empty: $y|
|:: $x for all $y?|
    :: pop from $y
    :: apply $x
|:: $x all $y| :: $x for all $y

|:: apply $x :stack empty: $y?|
|:: apply $x :item: $y|
    :: $x $y

|:: sum $x :@rpn data: $y| :total: $y
|:: sum $x? :total: $y|
    :@rpn: ($x $y +)
|:: sum $x?|
    :total: 0

||:: push 10 to numbers
  :: push 20 to numbers
  :: push 30 to numbers
  :: sum all numbers