Generate builtins section of the manual

doc/manual/src/expressions/builtins.md

@@ -1,68 +0,0 @@
-# Built-in Functions
-
-This section lists the functions built into the Nix expression
-evaluator. (The built-in function `derivation` is discussed above.)
-Some built-ins, such as `derivation`, are always in scope of every Nix
-expression; you can just access them right away. But to prevent
-polluting the namespace too much, most built-ins are not in
-scope. Instead, you can access them through the `builtins` built-in
-value, which is a set that contains all built-in functions and values.
-For instance, `derivation` is also available as `builtins.derivation`.
-
-  - `derivation` *attrs*; `builtins.derivation` *attrs*  
-
-    `derivation` is described in [its own section](derivations.md).
-
-  - `import` *path*; `builtins.import` *path*  
-
-    Load, parse and return the Nix expression in the file *path*. If
-    *path* is a directory, the file ` default.nix ` in that directory
-    is loaded. Evaluation aborts if the file doesn’t exist or contains
-    an incorrect Nix expression. `import` implements Nix’s module
-    system: you can put any Nix expression (such as a set or a
-    function) in a separate file, and use it from Nix expressions in
-    other files.
-
-    > **Note**
-    >
-    > Unlike some languages, `import` is a regular function in Nix.
-    > Paths using the angle bracket syntax (e.g., `import` *\<foo\>*)
-    > are [normal path values](language-values.md).
-
-    A Nix expression loaded by `import` must not contain any *free
-    variables* (identifiers that are not defined in the Nix expression
-    itself and are not built-in). Therefore, it cannot refer to
-    variables that are in scope at the call site. For instance, if you
-    have a calling expression
-
-    ```nix
-    rec {
-      x = 123;
-      y = import ./foo.nix;
-    }
-    ```
-
-    then the following `foo.nix` will give an error:
-
-    ```nix
-    x + 456
-    ```
-
-    since `x` is not in scope in `foo.nix`. If you want `x` to be
-    available in `foo.nix`, you should pass it as a function argument:
-
-    ```nix
-    rec {
-      x = 123;
-      y = import ./foo.nix x;
-    }
-    ```
-
-    and
-
-    ```nix
-    x: x + 456
-    ```
-
-    (The function argument doesn’t have to be called `x` in `foo.nix`;
-    any name would work.)