Function Definitions in Mojo
Functions are a core building block in any programming language, and Mojo introduces a familiar yet type-safe way of defining them. In this article, we’ll look at how to define functions, use typed parameters, and specify return types. If you’re coming from Python, you’ll find the syntax both intuitive and more explicit.
Basic Function Syntax
A simple function in Mojo is defined using the fn keyword, followed by the function name, typed parameters, and a return type:
fn greet(name: String) -> String:
return "Hello, " + nameIn this example:
name: Stringdefines the parameter and its type-> Stringdeclares the return type
Multiple Parameters
Mojo supports multiple typed parameters, just like Python but with stricter type safety:
fn add(a: Int, b: Int) -> Int:
return a + bReturn Types
You can explicitly define the type that the function should return. This improves performance and makes code easier to understand. If a function doesn’t return anything, you can use None:
fn log_message(msg: String) -> None:
print(msg)Default Parameter Values (Upcoming Feature)
As of current Mojo versions, default parameter values may not yet be supported, but the syntax may look similar to Python in future versions. Stay tuned to the official documentation.
Comparing with Python
Here’s a comparison of a function in Python vs Mojo:
| Python | Mojo |
|---|---|
def add(a, b): return a + b | fn add(a: Int, b: Int) -> Int: return a + b |
Summary
- Use
fnto define a function - Each parameter must include a type annotation
- Use
-> Typeto specify return values - Clear syntax improves performance and readability
In the next article, we’ll explore control structures like if, for, and while in Mojo.
I would like to put together a comparison between Python and Mojo next time.
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