# `Isbn`

An ISBN (ISO 2108) in its 13 digits with no hyphens, its check digit passing: `9780306406157`.

[Commerce and logistics](types.md#commerce-and-logistics); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `Isbn("9780306406157")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: Isbn)` reads one from its text; text that isn't one at all fails `malformed`, such as `9780306406158`, `0306406152` or `978-0-306-40615-7`.

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `9780306406157` | `"9780306406157"` |
| `9791090636071` | `"9791090636071"` |

It is stored in one column named for the field, of type `text`. `9791090636071` is stored as `'9791090636071'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `9780306406157` | `9780306406157` |
| `9791090636071` | `9791090636071` |

## Operations

It has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It isn't ordered, so `<` and sorting don't take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.