What are the fundamentals of Mojo?

Python is used as the fundamental language for developing artificial intelligence. However, it is too slow as compared to C++ or Rust because of its ability to offer manual memory management[object Object] and ownership systems.

For example, let’s have a look at the basic “Hello, world!” program for Mojo:

Note: Mojo was made public in May 2023 by a company called Modular. The person responsible is Chris Lattner who was also the brains behind Swift.

Mojo is a relatively newer programming language, and we will explore its features in this Answer. Let’s start with the basic language semantics.

Language structure

Mojo is based on Python and supports its syntax and semantics. It is typed exactly like Python, with the indentations for changing scopes, and even follows the same control-flow syntax for loop and conditional statements.

However, one key difference between the two is that Mojo allows us to statically set variables as well. This feature is an added security measure and can be invoked using the let and var keywords.

The let and var keywords

The simplest way to explain the difference between these two keywords is that the let keyword allows us to define variables that are immutable[object Object], while the var keyword allows us to define variables that are mutable[object Object]. The code block below demonstrates the execution of the two keywords. Try changing the keywords to see how it affects the output.

Note: You can read this Answer to learn more about the two keywords.

Now, let’s discuss a few more things introduced in the code snippets above. You may have noticed that we also set the type for our variable, x – this takes us to our next topic, which is typesetting.

Typesetting

Mojo allows us to set types for our variables, which acts as an added security measure for the language. A variable defined to be of a certain type can not take up a value of a different type. Unlike Mojo, Python allows flexible types and allows you to change variable types midway through code execution. Here is a demonstration of how we can use typesetting in Mojo:

Note: When we execute the above code, we get an error that we cannot assign a value of the StringLiteral type to a variable of the Int type. To learn more about the differences between Mojo and Python, please visit this Answer.

You may have noticed that instead of the usual def keyword in Python, we use the fn keyword to define the function. This keyword will be discussed in the following section.

The fn vs. def keywords

In the case of Mojo, both keywords can be used to define a function. However, the use of the fn keyword enforces Mojo’s rules and semantics. Using the def keyword to define a function allows us to use the Python ecosystem inside the function. In the code example below, we can see that when we try to execute native Python code inside a function defined using the fn keyword, we get an error. You should try resolving this error on your own.

Note: You can read this Answer to learn the differences between the two keywords.

MLIR

Mojo is one of the few programming languages that provides low-level support for Multi-Level Intermediate Representation (MLIR)—an extensible compiler infrastructure project designed to assist in the development of high-performance compilers and toolchains. Mojo provides direct access to low-level MLIR primitives required to create abstractions, allowing us to perform powerful yet zero-cost computations.

Note: To read more on MLIR, follow this Answer.

Mojo leverages MLIR, making programming on GPUs running CUDA and other accelerators easier. This allows for scaling to exotic hardware types without much complexity.

Conclusion

Mojo is a promising and innovative programming language that brings together the best of both worlds: the ease of Python with the scalability and robustness of languages like C++ and Rust. In this Answer, we explored some of the key features and concepts introduced by Mojo and shed light on its unique capabilities.