# Prelude This package contains useful utilities for getting started with the Dhall configuration language. The Prelude is unique in that changes are approved by the same process as changes to the language standard. ## Usage The Prelude is hosted at: * [https://prelude.dhall-lang.org/](https://prelude.dhall-lang.org) ... which you can use in several ways: * To browse the latest release of the Prelude package, you can visit: [https://prelude.dhall-lang.org/](https://prelude.dhall-lang.org) * To import a specific expression add the path to that expression to the URL For example, the URL for the `./Bool/not` expression is: [https://prelude.dhall-lang.org/Bool/not](https://prelude.dhall-lang.org/Bool/not) Here is an example of using the [`./Bool/not`](./Bool/not) expression: ```dhall let Bool/not = https://prelude.dhall-lang.org/Bool/not in Bool/not True ``` * To import the entire Prelude as a nested record, use the following import within your Dhall code: [https://prelude.dhall-lang.org/package.dhall](https://prelude.dhall-lang.org/package.dhall) Here is an example of accessing the [`./Bool/not`](./Bool/not) expression as a field of that record: ```dhall let Prelude = https://prelude.dhall-lang.org/package.dhall in Prelude.Bool.not True ``` * You can pin an expression to a specific version of the Prelude by prefixing the path with the Prelude version For example, you could use the following URL to import version `10.0.0` of the Prelude: [https://prelude.dhall-lang.org/v10.0.0/package.dhall](https://prelude.dhall-lang.org/v10.0.0/package.dhall) This also works for individual expressions, too, such as: [https://prelude.dhall-lang.org/v10.0.0/Bool/not](https://prelude.dhall-lang.org/v10.0.0/Bool/not) ... or for browsing a specific release of the Prelude: [https://prelude.dhall-lang.org/v10.0.0](https://prelude.dhall-lang.org/v10.0.0) The `prelude.dhall-lang.org` domain is CORS-enabled so the Prelude can be used as a transitive import of other packages without violating the Dhall language's CORS check. ## Scope There is no hard rule for what belongs in the Prelude, but we can document what we have included so far: * General purpose utilities (like [`./List/filter`](./List/filter)) * Re-exports of language built-ins (like [`./Natural/fold`](./Natural/fold)) * Integrations with other configuration formats (like [`./JSON/package.dhall`](./JSON/package.dhall)) The [contributing instructions](../.github/CONTRIBUTING.md#how-do-i-change-the-language) provide more details about how to discuss or propose changes if you would like to contribute to the Prelude.