# `Ratio`

One number to another, as written: `16:9`.

Use it to record a proportion as people say it, such as a recipe's ratio. `16:9` and `32:18` stay two different values. For a share of a whole, use [`Percentage`](/docs/types/type-percentage.md). For screens, use [`AspectRatio`](/docs/types/type-aspect-ratio.md).

## Shape

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

## Example

```jadpo
Ratio { numerator: 16.0 denominator: 9.0 }
```

`text.parse(raw, as: Ratio)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `16/9`, `16 : 9` or `16:`.

## Good to know

- `==` 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
"16:9"
"1.85:1"
"4.0:3.0"
```

## Details

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

`Ratio` 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: `16:9`, `1.85:1` and `4.0:3.0`.

### How it is stored

It is stored in 2 columns, each named for the field, `_` and its suffix. This is `1.85:1`:

| Column | Type | Holds |
|---|---|---|
| `<field>_numerator` | `numeric` | `1.85` |
| `<field>_denominator` | `numeric` | `1` |

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `16:9` | `16:9` |
| `1.85:1` | `1.85:1` |
| `4.0:3.0` | `4.0:3.0` |

### 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>