The `Decimal` type provides exact decimal arithmetic backed by `java.math.BigDecimal`. Use it instead of `Float` when rounding errors are unacceptable (financial calculations, invoices, rates).

```vary-snippet
from decimal import parse, from_int, round_half_up

let price = parse("19.99").unwrap()
let qty = from_int(3)
let total = price * qty                      # 59.97 (exact)
let tax = total.divide(from_int(100), 2, round_half_up)
```

## Constructors

| **Function** | **Returns** | **Description** |
|----------|-----------|-------------|
| `parse(s)` | `Result[Decimal, DecimalError]` | Parse a string into a Decimal |
| `from_int(n)` | `Decimal` | Create a Decimal from an integer |
| `from_float(n)` | `Decimal` | Create from float (prefer `parse` for exact values) |

## Operators

Decimal supports `+`, `-`, `*`, and comparison operators (`==`, `!=`, `<`, `>`, `<=`, `>=`).

Division requires explicit scale and rounding mode:

```vary-snippet
let result = a.divide(b, scale, mode)
let rounded = d.quantize(scale, mode)
```

## Rounding modes

| **Constant** | **Description** |
|----------|-------------|
| `round_half_up` | Rounds 0.5 away from zero; for invoices |
| `round_half_even` | Banker's rounding; minimizes bias |
| `round_down` | Truncate toward zero; never exceeds |
| `round_up` | Round away from zero; never undershoots |