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# File hierarchy

Modules can be mapped to a file/directory hierarchy. Let's break down the visibility example in files:

    $ tree .
    .
    ├── my
    │   ├── inaccessible.rs
    │   └── nested.rs
    ├── my.rs
    └── split.rs

In `split.rs`:

    // This declaration will look for a file named `my.rs` and will
    // insert its contents inside a module named `my` under this scope
    mod my;

    fn function() {
        println!("called `function()`");
    }

    fn main() {
        my::function();

        function();

        my::indirect_access();

        my::nested::function();
    }

In `my.rs`:

    // Similarly `mod inaccessible` and `mod nested` will locate the `nested.rs`
    // and `inaccessible.rs` files and insert them here under their respective
    // modules
    mod inaccessible;
    pub mod nested;

    pub fn function() {
        println!("called `my::function()`");
    }

    fn private_function() {
        println!("called `my::private_function()`");
    }

    pub fn indirect_access() {
        print!("called `my::indirect_access()`, that\n> ");

        private_function();
    }

In `my/nested.rs`:

    pub fn function() {
        println!("called `my::nested::function()`");
    }

    #[allow(dead_code)]
    fn private_function() {
        println!("called `my::nested::private_function()`");
    }

In `my/inaccessible.rs`:

    #[allow(dead_code)]
    pub fn public_function() {
        println!("called `my::inaccessible::public_function()`");
    }

Let's check that things still work as before:

    $ rustc split.rs && ./split
    called `my::function()`
    called `function()`
    called `my::indirect_access()`, that
    > called `my::private_function()`
    called `my::nested::function()`