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Merge pull request #343 from jherland/nix-language-readthrough

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Nix language tutorial: fix typos, add notes
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Valentin Gagarin 2022-10-27 10:06:15 +02:00 committed by GitHub
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source/tutorials/nix-language.md
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@ -852,7 +852,7 @@ Example:
/absolute/path
Paths are relative when they contain at least one slash (`/`) but to not start with one.
Paths are relative when they contain at least one slash (`/`) but do not start with one.
They evaluate to the path relative to the file containing the expression.
The following examples assume the containing Nix file is in `/current/directory` (or `nix repl` is run in `/current/directory`).
@ -905,6 +905,10 @@ Example:
/current
:::{note}
Paths can be used in antiquotation – an [impure operation](impurities) we will cover in detail in a [later section](path-impurities).
:::
#### Search path
Also known as “angle bracket syntax”.
@ -1043,7 +1047,7 @@ x: x + 1
The `<LAMBDA>` indicates the resulting value is an anonymous function.
We can assign functions a name as to any other value.
As with any other value, functions can be assigned to a name.
Example:
@ -1453,6 +1457,7 @@ Nix supports other types of impure expressions, such as [search paths](search-pa
We do not cover those here in more detail, as they do not matter for how the Nix language works in principle, and because they are discouraged for the very reason of breaking reproducibility.
:::
(path-impurities)=
### Paths
Whenever a file system path is rendered to a character string with [antiquotation](antiquotation), the contents of that file are copied to a special location in the file system, the *Nix store*, as a side effect.
@ -1491,6 +1496,8 @@ It is an error if the file system path does not exist.
</details>
For directories the same thing happens: The entire directory (including nested files and directories) is copied to the Nix store, and the evaluated string becomes the Nix store path of the directory.
### Fetchers
Files to be used as build inputs do not have to come from the file system.
@ -1650,7 +1657,8 @@ Explanation:
It returns an attribute set.
- The argument must at least have the attributes `config` and `pkgs`, and may have more attributes.
- The returned attribute set contains the attributes `imports` and `environment`.
`imports` is a list with one element: a path to a file next to this Nix file, called `hardware-configuration.nix`.
- `imports` is a list with one element: a path to a file next to this Nix file, called `hardware-configuration.nix`.
When evaluated, the `./hardware-configuration.nix` will be copied into the Nix store, converting it into a Nix store path.
:::{note}
`imports` is not the impure built-in `import`, but a regular attribute name!