Using Motoko base modules

The design of Motoko strives to minimize built-in types and operations. Instead of built-in types, Motoko provides a base library of modules to handle many kinds of common operations and make the language feel complete. This base library is still evolving with modules that support core features and all of the base library APIs are subject to change over time to varying degrees. You should note, in particular, that the size and number of modules and functions included in the base library is likely to increase dramatically and updates to the base library modules might introduce breaking changes that require you to update your programs to remain compatible.

Importing from the base library

To import from the base library, use the import keyword followed by a local module name and a URL where the import declaration can find the module you want to import. For example:

import Debug "mo:base/Debug";
Debug.print("hello world");

This example illustrates how to import Motoko code—indicated by using the mo: prefix—using the base/ base library path and the module name Debug. You can also import Motoko code and other modules using relative paths. For example, if you have created a Motoko program named types.mo in the same folder as your main program, you could include it with an import declaration like this:

import Types "./types";

Viewing the base library modules

You can find source code and documentation for Motoko base modules in the motoko-base open source repository. There are instructions in the repository for generating a local copy of the current documentation for the Motoko base library.

You can also search for documentation by using Search in any page of the Developer Center.