# Fifth Stack

A simple stack-based language called Fifth

## Usage

```shell
python fifth_stack.py
```

### Commands

- `PUSH <n>` - push integer onto stack
- `POP` - remove top element
- `SWAP` - swap top two elements
- `DUP` - duplicate top element
- `+`, `-`, `*`, `/` - arithmetic operations
- `EXIT` - quit

### Example

```
stack is []
PUSH 3
stack is [3]
PUSH 11
stack is [3, 11]
+
stack is [14]
DUP
stack is [14, 14]
PUSH 2
stack is [14, 14, 2]
*
stack is [14, 28]
SWAP
stack is [28, 14]
/
stack is [2]
+
ERROR: two numbers required
POP
stack is []
EXIT
```

## Tests

```bash
pip install pytest
pytest -v test_fifth_stack.py
```

## Requirements

- Python 3.10+
- pytest