Defining Modules

In this section, we’ll talk about modules and other parts of the module system, namely paths that allow you to name items and the use keyword that brings a path into scope.

Here we provide a quick reference on how modules, paths, and the use keyword work in the compiler, and how most developers organize their code. We’ll be going through examples of each of these rules throughout this chapter, but this is a great place to refer to as a reminder of how modules work.

Start from the package root: When compiling a package, the compiler first looks for code to compile in the package root file, which is src/lib.pnt for a library package or src/contract.rs for a contract package.
Declaring modules: You can declare new modules by creating files for them in the appropriate directories. Say you want to declare a new garden module. You have two options:
- You can create the file src/garden.pnt if you want the garden module to be a single file module. That is, if you don't want the module garden to have submodules.
- You can create the file src/garden/garden.pnt if you want the module to be a multi-file module. That is, if you want the module garden to have submodules. The submodules of garden would then live in the src/garden directory.
Declaring submodules: In any directory other than the package root directory, you can create new submodules. For example, say you want to declare a submodule of garden named vegetables. You have two options:
- You can create the file src/garden/vegetables.rs if you want the vegetables submodule to be a single file submodule. That is, if you don't want the submodule vegetables to have its own submodules.
- You can create the file src/garden/vegetables/vegetables.rs if you want the vegetables submodules to be a multi-file submodule. That is, if you want the submodule vegetables to have its own submodules.
Paths to code in modules: Once a module is part of your package, you can refer to code in that module from anywhere else in the same package. For example, an enum Asparagus in the garden vegetables module would be found at ::garden::vegetables::Asparagus.
The use keyword: Within a Pint file, the use keyword creates shortcuts to items to reduce repetition of long paths. For example, you can create a shortcut to ::garden::vegetables::Asparagus using the statement use ::garden::vegetables::Asparagus; declared at global scope in a Pint file. From then on, you only need to write Asparagus to make use of that enum in this file.

Here, we create a contract package named backyard that illustrates these rules. The package's directory, also named backyard, contains these files and directories:

backyard
├── pint.toml
└── src
    ├── contract.pnt
    └── garden
        ├── garden.rs
        └── vegetables.rs

The package root file is src/contract.rs since this is a contract package. It contains:

use garden::vegetables::Asparagus;

predicate Foo {
    var green_asparagus = Asparagus::Green;
}

The submodule vegetables which is defined in src/garden/vegetables.pnt, contains:

enum Asparagus = Green | White | Purple;

The Book of Pint

Defining Modules

Modules Cheat Sheet