# `Fraction`

An exact fraction as written: `3/4`.

Use it for numbers people say as fractions, such as a share in a property. `1/2` and `2/4` stay two different values. For a percentage, use [`Percentage`](/docs/types/type-percentage.md).

## Shape

| Field | Type | Required? |
|---|---|---|
| `numerator` | `Int` | Yes |
| `denominator` | `Int` | Yes |

## Example

```jadpo
Fraction { numerator: 3 denominator: 4 }
```

`text.parse(raw, as: Fraction)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `3/0`, `3` or `3 / 4`.

## Good to know

- `denominator` must be at least 1, so a negative fraction has a negative numerator.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it, so sort by one of its parts instead.

## In JSON

A string, in a request, a response or `json.write`:

```json
"3/4"
"-1/2"
"30000/1001"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`Fraction` is in the group Maths and data, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `3/4`, `-1/2` and `30000/1001`.

### How it is stored

It is stored in 2 columns, each named for the field, `_` and its suffix. This is `-1/2`:

| Column | Type | Holds |
|---|---|---|
| `<field>_numerator` | `bigint` | `-1` |
| `<field>_denominator` | `bigint` | `2` |

### How it is shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `3/4` | `3/4` |
| `-1/2` | `-1/2` |
| `30000/1001` | `30000/1001` |

### Operations

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>