Mojo (programming language)

Mojo

Paradigm	Multi-paradigm: imperative (primary) functional generic
Family	Python
Designed by	Chris Lattner
Developer	Modular Inc.
First appeared	2023 (2023)
Preview release	24.2.1 / April 12, 2024 (2024-04-12)
Typing discipline	Affine inferred nominal duck static dynamic strong
OS	Cross-platform
License	Proprietary
Filename extensions	.🔥 (the fire emoji/U+1F525 Unicode character), alternatively .mojo
Website	www.modular.com/mojo
Influenced by
Python, Cython, C, C++, Rust, Swift, Zig

Mojo is a proprietary programming language that is currently under development. It is available both in browsers via Jupyter notebooks, and locally on both Linux and macOS. Mojo combines the usability of Python with its syntax (and aims to become a superset of it) with the high performance of languages like C.

Origin, design and development

• In 2022, the Modular company was founded by Chris Lattner, the original architect of the Swift programming language and LLVM, and Tim Davis, a former Google employee.

• In September 2022, an initial build of Mojo was released internally by Modular Inc.

• In January 2024, an inference model of LLaMA2 written in Mojo was released to the public.

Features

• Mojo uses LLVM and MLIR as its compilation backend.

• Mojo uses inferred static typing.

• Mojo was created for easy transition from Python. The language has syntax similar to Python's, and allows users to import Python modules.

• Mojo is not open source, but it is planned to become open source in the future.

• Mojo has a borrow checker, an influence from Rust.

• Mojo plans to add a foreign function interface to call C/C++ and Python code.

• Mojo is not source-compatible with Python 3, only providing a subset of its syntax, e.g. missing the global keyword, list and dictionary comprehensions, and support for classes. Further, Mojo also adds features that enable performant low-level programming: fn for creating typed, compiled functions and "struct" for memory-optimized alternatives to classes. Mojo structs support methods, fields, operator overloading, and decorators.

• Mojo def functions use value semantics by default (functions receive a copy of all arguments and any modifications are not visible outside the function), while Python functions use reference semantics (functions receive a reference on their arguments and any modification of a mutable argument inside the function is visible outside).

• Mojo files use the .🔥 or .mojo file extension.

Programming examples

In Mojo, functions can be declared using both fn (for performant functions) or def (for Python compatibility).

Basic arithmetic operations in Mojo with a def function:

def sub(x, y):
    """A pythonic subtraction."""
    res = x - y
    return res

and with an fn function:

fn add(x: Int, y: Int) -> Int:
    """A rustacean addition."""
    let res: Int = x + y
    return res

The manner in which Mojo employs var and let for mutable and immutable variable declarations respectively mirrors the syntax found in Swift. In Swift, var is used for mutable variables, while let is designated for constants or immutable variables.

Variable declaration and usage in Mojo:

fn main():
    let x = 1
    
    let y: Int
    y = 1

    var z = 0
    z += 1

Usage

The Mojo SDK allows Mojo programmers to compile and execute Mojo source files locally from the command line and currently supports Ubuntu and macOS. Additionally, there is a Mojo extension for Visual Studio Code which provides code completion and tooltips.

See also

• List of programming languages for artificial intelligence
• Python
• Nim
• Ring
• Carbon
• Zig
• Julia
• Rust

External links

• Official website
• Mojo manual
• mojo on GitHub
• All about mojo programming language
• Introduction to Mojo programming language
• Mojo may be the biggest programming language advance in decades
• Mojo: The Future of AI Programming