Move module evaluation discussion to a new lesson.

lessons/001-a-module/lesson.md

@@ -102,55 +102,12 @@ Option definitions are generally straight-forward bindings of values to option n
 }
 ```
 
-## Function Arguments
-
-### FIXME: Talk about the automatically provided arguments
-
-## Evaluation
-
-### FIXME: Talk about evalModules
-
 Note that our option declarations and option definitions do not need to exist in the same file.
 When we evaluate our modules, we can simply include both files.
 As long as every definition has a declaration, we can successfully evaluate our modules.
 If there is an option definition that has not been declared, the module system will throw an error.
 
-# ***OLD***
-
-In the [eval][eval] file, we have declared an attrset called `mymodule` which is composed of 3
-fields: `imports`, `options` and `config`. This is a module with default values for those fields.
-You can omit any of those fields and they will use those same default values.
-
-[//]: # (./eval.nix)
-
-If you execute the run file (`./run`), you will see printed the empty JSON object `{}`.
-
-[eval]: ./eval.nix
-
-## Module Fields
-
-The `options` field lets you define variables that can be used in the `config` section.
-
-The `config` field assigns values to options defined in other modules. We call this using an option.
-
-The `imports` field lets you import other modules from a module.
-
-We will see what goes in those fields in later lessons.
-
-## Evaluating Modules
-
-In the [eval][eval] file, we use a function called `evalModules`. This function takes an attrset as
-argument which can contain the field named `modules`. In there, we can put as many module as we
-want.
-
-`evalModules` will then merge all `imports`, `options` and `config` fields of all given modules
-following some rules we will see in the next lessons. It then produces an attrset whose only
-interesting field - the result of merging all modules - is found in the `config` field. This is the
-one we print when executing the `./run` file.
-
-## Nixpkgs
+## Function Arguments
 
-The vast majority of nixpkgs is made out of modules, all merged together in the top-level
-`evalModules`.
+### FIXME: Talk about the automatically provided arguments
 
-[option-types-basic]: https://nixos.org/manual/nixos/stable/#sec-option-types-basic

lessons/module-evaluation/lesson.md

@@ -0,0 +1,39 @@
+# Module Evaluation
+
+In the [eval][eval] file, we have declared an attrset called `mymodule` which is composed of 3
+fields: `imports`, `options` and `config`. This is a module with default values for those fields.
+You can omit any of those fields and they will use those same default values.
+
+[//]: # (./eval.nix)
+
+If you execute the run file (`./run`), you will see printed the empty JSON object `{}`.
+
+[eval]: ./eval.nix
+
+## Module Fields
+
+The `options` field lets you define variables that can be used in the `config` section.
+
+The `config` field assigns values to options defined in other modules. We call this using an option.
+
+The `imports` field lets you import other modules from a module.
+
+We will see what goes in those fields in later lessons.
+
+## Evaluating Modules
+
+In the [eval][eval] file, we use a function called `evalModules`. This function takes an attrset as
+argument which can contain the field named `modules`. In there, we can put as many module as we
+want.
+
+`evalModules` will then merge all `imports`, `options` and `config` fields of all given modules
+following some rules we will see in the next lessons. It then produces an attrset whose only
+interesting field - the result of merging all modules - is found in the `config` field. This is the
+one we print when executing the `./run` file.
+
+## Nixpkgs
+
+The vast majority of nixpkgs is made out of modules, all merged together in the top-level
+`evalModules`.
+
+[option-types-basic]: https://nixos.org/manual/nixos/stable/#sec-option-types-basic

site/mkdocs.yml

@@ -9,6 +9,7 @@ nav:
   - Lessons:
     - Getting Started:
       - lessons/001-a-module/lesson.md
+      - lessons/module-evaluation/lesson.md
     - Types:
       - lessons/010-basic-types/lesson.md
       - lessons/composed-types/lesson.md