The Ultimate Guide to Rust Programming/

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Variable and Parameter Scope

Variable and Parameter Scope

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Let’s look at one of our examples from earlier:

Rust 1.40.0
fn say_apples(apples: i32) {
    println!("I have {} apples", apples);
}
fn main() {
    say_apples(10);
}

We have apples in the parameter list for say_apples. This means that we’re allowed to use the name apples inside the body of the say_apples function. However, we can’t use it inside the body of the main function. This program will not compile:

Rust 1.40.0
fn say_apples(apples: i32) {
    println!("I have {} apples", apples);
}
fn main() {
    say_apples(10);
    println!("apples == {}", apples);
}

Variable names are only visible inside a certain scope. When you have the function ...