nimnimnim.nim

import strutils
import sequtils

type
    Node[T] = object
        Item: T
        Next: ref Node[T]
    Stack[T] = object
        Top: ref Node[T]
        Size: int
    ElemKind = enum
        Number,
        Operator
    Elem = object
        case Kind: ElemKind
        of Number: value: int
        of Operator: optype: char

proc Size[T](stack: Stack[T]): int = 
    return stack.Size

proc Push[T](stack: var Stack[T], i: T) =
    var n = new(Node[T])
    n.Item = i
    n.Next = stack.Top
    stack.Top = n
    stack.Size = stack.Size + 1

proc Pop[T](stack: var Stack[T]): T =
    result = stack.Top.Item
    stack.Top = stack.Top.Next
    stack.Size = stack.Size - 1

proc `--` (front: seq[Elem], i: int): seq[Elem] = concat(front,@[Elem(Kind: Number, value: i)])
proc `--` (front: seq[Elem], c: char): seq[Elem] = concat(front,@[Elem(Kind: Operator, optype: c)])


var prog = @[] -- 3 -- 3 -- '+' -- 7 -- '*'
var stack = Stack[int]()

for i in prog:
    case i.Kind
    of Number:
        stack.Push(i.value)
    of Operator:
        case i.optype
        of '+':
            stack.Push(stack.Pop() + stack.Pop())
        of '*':
            stack.Push(stack.Pop() * stack.Pop())
        else:
            stdout.writeln("UH OH")

stdout.writeln(stack.Pop())