Rust - Package

The terms:

• crate: A crate is a binary or library.
• crate root: The crate root is a source file that the Rust compiler starts from and makes up the root module (named crate) of your crate module tree.

• package: A package is one or more crates that provide a set of functionality. A package contains a Cargo.toml file that describes how to build those crates.

  A package could be one of the following cases:

  • One or more binary crates
  • One library crate with zero or more binary crates

  Because:

  A package must contain zero or one library crates, and no more. It can contain as many binary crates as you’d like, but it must contain at least one crate (either library or binary)

• module: A module is a piece of code wrapped by mod keyword (potentially prefixed pub). Modules let us organize code within a crate into groups for readability and easy reuse. Modules also control the privacy of items, which is whether an item can be used by outside code (public) or is an internal implementation detail and not available for outside use (private).

• pub: pub makes a module, struct, member of struct, fn, enum, .etc be available to be used by outside code (public).

  NOTE: By default, when the enum is marked to be pub, all its variants are pub by default.

  pub can be used together with use (e.g. pub use crate::Foo;) to re-exporting some items from current scope. This technique is always used inside src/lib.rs library crate root to export the items defined in other modules in the same directory.

  E.g.

  src/lib.rs:

    mod foo;
    pub use foo::Foo;
  

  src/foo.rs:

    struct Foo {
        //...
    }