# `Doi`

A digital object identifier (the DOI Handbook), with no resolver before it and ASCII letters in lower case: `10.1038/nphys1170`.

[Software](types.md#software); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `Doi("10.1000/182")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: Doi)` reads one from its text; text that isn't one at all fails `malformed`, such as `doi:10.1000/182`, `https://doi.org/10.1000/182` or `10.1038/NPHYS1170`.

## 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 |
|---|---|
| `10.1000/182` | `"10.1000/182"` |
| `10.1038/nphys1170` | `"10.1038/nphys1170"` |
| `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` | `"10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o"` |
| `10.1000.10/123456` | `"10.1000.10/123456"` |

It is stored in one column named for the field, of type `text`. `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` is stored as `'10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `10.1000/182` | `10.1000/182` |
| `10.1038/nphys1170` | `10.1038/nphys1170` |
| `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` | `10.1002/(sici)1097-4571(199806)49:8<693::aid-asi4>3.0.co;2-o` |
| `10.1000.10/123456` | `10.1000.10/123456` |

## 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.