Mojo (programming language)

The Mojo programming language was created by Modular Inc, which was founded by Chris Lattner, the original architect of the Swift programming language and LLVM, and Tim Davis, a former Google employee.^[16] The intention behind Mojo is to bridge the gap between Python’s ease of use and the fast performance required for cutting-edge AI applications.^[17]

According to public change logs, Mojo development goes back to 2022.^[18] In May 2023, the first publicly testable version was made available online via a hosted playground.^[19] By September 2023 Mojo was available for local download for Linux^[20] and by October 2023 it was also made available for download on Apple's macOS.^[21]

In March 2024, Modular open sourced the Mojo standard library and started accepting community contributions under the Apache 2.0 license.^[22][23]

Mojo was created for an easy transition from Python. The language has syntax similar to Python's, with inferred static typing,^[24] and allows users to import Python modules.^[25] It uses LLVM and MLIR as its compilation backend.^[6][26][27] The language also intends to add a foreign function interface to call C/C++ and Python code. The language 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.^[28]

The language also provides a borrow checker, an influence from Rust.^[29] 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).^[30]

The language is not open source, but it is planned to be made open source in the future.^{[31][10][32][33]}

In Mojo, functions can be declared using both fn (for performant functions) or def (for Python compatibility).^[25]

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.^[25]

Variable declaration and usage in Mojo:

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

    var z = 0
    z += 1

• List of programming languages for artificial intelligence