finished ch7

.obsidian/workspace.json

@@ -34,9 +34,23 @@
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               "title": "Modules and Use"
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@@ -178,15 +192,16 @@
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-    "Modules and Use.md",
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Collection of Common Data Structs.md

@@ -0,0 +1 @@
+# Collection of Common Data Structs

Modules and Use.md

@@ -220,3 +220,55 @@ This makes it harder to tell what names are used in scope and where a name in us
 This is often used when testing to bring everything under test into the tests module
 
 This is also used as part of the prelude pattern
+
+
+## Modules In External Files
+This works for both binary and library crates
+
+leave only the mod definition in the crate root
+```rust
+mod example_mod;
+```
+
+then place the code that you want inside another file called example_mod.rs
+```rust
+pub mod inner_example_mod {
+	pub fn example_fn () {
+	}
+} 
+```
+
+you only need to to load a file using a ``mod`` declaration once in your module tree
+
+The compiler will know the file is part of the project because of the mod declaration
+
+mod is no an "include" operation like in C/C++ or python
+
+you can then separate inner_example_mod into its own file called inner_example.rs
+```rust
+pub fn example_fn () {}
+```
+
+### Alternate File Patrhs
+So far only use idiomatic file paths but you can also use older style of file paths. The compiler will also look for a module named front_of_house declared in the crate root, the compiler will look for the module’s code in:
+
+- src/front_of_house.rs (what we covered)
+- src/front_of_house/mod.rs (older style, still supported path)
+- 
+For a module named ``inner_example_mod`` that is a submodule of ``front_of_house``, the compiler will look for the module’s code in:
+
+- src/front_of_house/inner_example_mod.rs (what we covered)
+- src/front_of_house/hosting/mod.rs (older style, still supported path)
+
+If you mix both styles for the same module then you will get a compiler error
+
+Using a mix of both styles for different modules is allowed but you will end up with many mod.rs files which can be confusing
+
+No matter which style is used it will not change how the use path is setup
+
+My preferred style:
+
+- In the file _src/example_mod.rs_
+	- In the file _src/example_mod/mod.rs
+		- Only use if it makes sense
+- In the file _src/example_mod/inner_example_mod.rs_