---
title: Functions
description: Defining execution blocks with C-style ergonomics and Rust-powered safety.
icon: SquareFunction
---

Functions are the primary unit of execution in Mist. They prioritize a traditional declaration order, placing the return type before the identifier to ensure signatures remain easy to scan in complex systems.

## Basic Syntax

A standard function requires a return type, a name, and a body. Use the `void` keyword for functions that do not return a value.

```mist
i32 add(i32 a, i32 b) {
    return a + b;
}

void log_status(str* message) {
    println!("{}", message);
}
```

## Visibility & Exports

Functions are private to their module by default. The `public` modifier exports the function for cross-module access.

```mist
public i32 get_version() {
    return 1;
}
```

## Mutable Parameters

Parameters follow Rust’s ownership rules but use Mist’s local variable syntax. Use `mut` to allow a function to modify its local binding of a value.

```mist
void update_score(i32 mut current_score, i32 bonus) {
    current_score = current_score + bonus;
}
```

## Generics & Lifetimes

Mist integrates type abstraction and memory management into a single generic block. Lifetimes and type parameters share the `< >` bracket following the identifier.

```mist
public str'a* choose_longer<'a, T: Display>(str'a* s1, str'a* s2, T meta) {
    println!("Metadata: {}", meta);
    return if (s1.len() > s2.len()) { s1 } else { s2 };
}
```

## Attributes & Metadata

Metadata is applied via the `#[attr]` syntax directly above the declaration for compiler hints or testing.

```mist
#[inline]
public bool is_active(u32 id) {
    return id > 0;
}
```

## Key Characteristics

* **Scannable Signatures:** Placing return types first allows for rapid identification of a function's output.
* **Unified Abstraction:** Lifetimes and type constraints are declared in one location, reducing signature noise.
* **Zero-Cost Mapping:** Every function maps directly to a Rust `fn`, maintaining performance and ecosystem compatibility.