{
  "machine": "Counter",
  "sigma": [
    "+",
    "-"
  ],
  "stackAlpha": [
    "1",
    "Z"
  ],
  "states": [
    {
      "id": "s1",
      "x": 260,
      "y": 260,
      "name": "balance"
    },
    {
      "id": "s2",
      "x": 580,
      "y": 260,
      "name": "settled"
    }
  ],
  "startId": "s1",
  "accepts": [
    "s2"
  ],
  "transitions": [
    {
      "id": "t1",
      "from": "s1",
      "to": "s1",
      "symbol": "+",
      "pop": "ε",
      "push": "1"
    },
    {
      "id": "t2",
      "from": "s1",
      "to": "s1",
      "symbol": "-",
      "pop": "1",
      "push": "ε"
    },
    {
      "id": "t3",
      "from": "s1",
      "to": "s2",
      "symbol": "ε",
      "pop": "Z",
      "push": "Z"
    }
  ],
  "notes": [
    {
      "id": "n1",
      "x": 180,
      "y": 80,
      "color": "blue",
      "anchorStates": [],
      "anchorTransitions": [],
      "text": "A bank account with one rule: never go below zero, and end settled at exactly zero. Every + deposits a token on the counter, every − withdraws one. A withdrawal with nothing on the counter gets stuck — overdraft rejected."
    },
    {
      "id": "n2",
      "x": 180,
      "y": 400,
      "color": "green",
      "anchorStates": [],
      "anchorTransitions": [],
      "text": "The ε move to settled only fires when the counter shows bottom Z, i.e. balance is exactly 0. One counter is all it takes to leave the world of finite automata."
    }
  ],
  "config": {
    "pdaParadigm": "explicit"
  },
  "meta": {
    "title": "Bank account: never overdrawn",
    "blurb": "Deposits (+) and withdrawals (−) where the balance never goes negative and ends at exactly zero. One counter separates this from anything a DFA could ever check.",
    "inputs": [
      {
        "w": "+-",
        "expect": "accept"
      },
      {
        "w": "++--",
        "expect": "accept"
      },
      {
        "w": "+-+-",
        "expect": "accept"
      },
      {
        "w": "+--+",
        "expect": "reject",
        "label": "overdraft"
      },
      {
        "w": "++-",
        "expect": "reject",
        "label": "money left"
      },
      {
        "w": "-",
        "expect": "reject"
      }
    ],
    "library": {
      "author": {
        "login": "thethinkmachine"
      },
      "license": "CC-BY-4.0",
      "tags": [
        "showcase",
        "counter"
      ],
      "difficulty": "intermediate"
    }
  },
  "format": "automata-studio/workspace",
  "schema": 1,
  "app": "dev"
}