Control Structures - Rust Programming

Functions are commonly used in Rust code, with the main function being a key element and entry point for many programs. The fn keyword is used to create new functions.

Syntax:
```rust
fn function_name(parameter_name: parameter_type) -> return_type {
    // code block
}
```


For example:
```rust
fn add(a: i32, b: i32) -> i32 {
    a + b
}
```

Functions - Rust Programming

By default, variables in Rust are immutable, meaning their value cannot be changed once assigned. To allow a variable to be mutable, the keyword "mut" must be used when declaring the variable.

Immutable example:
```rust
let x = 5;
```
This declares a variable named "x" and assigns it the value of 5. The type of x is inferred by the compiler to be i32.

Mutable example:
```rust
let mut y = 10;
y = 20;
```
This declares a mutable variable "y" with an initial value of 10 and then changes the value to 20.

University of Michigan - Ann Arbor

In Rust, a variable is a container that stores a value of a specific data type. Variables are declared using the keyword "let" and must be assigned a value when they are declared. 

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