Rant supports basic dependency management via a module system. Modules are libraries of Rant functions that you can write and load into other Rant programs for use. Each module resides in its own source file.

Writing modules

A module is simply a Rant program that returns a map containing the module's contents. Similar to a regular Rant program, modules are expected have the .rant file extension.

Below is a basic example of a very simple module:

# seq.rant

<%module = (::)>

[$module/fib: n] {
  (:) [rep: <n>] { @edit f: <f> (<f/-2 ? 0> + <f/-1 ? 1>) }


Importing and using modules

A module can be imported using the @require keyword or, less commonly, the [require] stdlib function. For this example, we'll import the seq module previously shown.

# Looks for `seq.rant` and imports it as map variable `seq`.
# You don't need to specify the file extension.
@require "seq"

# Call the `[fib]` function from the module
[seq/fib: 16]
# -> (: 1; 1; 2; 3; 5; 8; 13; 21; 34; 55; 89; 144; 233; 377; 610; 987)

Imported modules are cached by the Rant context running the program. If you import the same module twice, it will be fetched from cache.

Compiler errors in modules

Rant needs to compile modules before they can be imported. If a module fails to compile, a runtime error will be triggered with the compiler error list.

Where Rant looks for modules

When you use @require, Rant looks for the module in the following locations in-order:

  1. The requesting program's file location
    • Skipped if the program was not loaded from a file
  2. The local modules path
    • Defaults to the current working directory, but the host app can reconfigure it
  3. The global modules path
    • Set by the RANT_MODULES_PATH environment variable
    • Can be disabled by the host app

If Rant cannot locate a module with a matching path and name, it will trigger a runtime error.

Relative paths in @require

@require can also accept a relative path to a module. This makes it possible to access modules in subfolders of any of the module search locations.

For example, if your application has a rant_modules subfolder in its main directory, you can import modules from it like this:

# Imports `my-module`
@require "rant_modules/my-module"