Rustを学びます

勉強ページは日本語ドキュメント参考
プログラミング言語Rust

Rustの日本語ドキュメント 2nd Edition
https://doc.rust-jp.rs/book/second-edition/

オリジナル
https://doc.rust-lang.org/book/

3. Common Programming Concepts

3.5 フロー制御

if!!

fn main(){

    let number = 3;

    if number < 5 {
        println!("condition was true");
    }else{
        println!("condition was false");
    }

}

条件式はboolのみです。0とか1を代用できません。
“`rust
fn main(){

let number = 1;

if number  {
    println!("condition was true");
}else{
    println!("condition was false");
}

}

===
error[E0308]: mismatched types
–> src/main.rs:5:8
|
5 | if number {
| ^^^^^^ expected bool, found integer
|
= note: expected type bool
found type {integer}

error: aborting due to previous error

let文内でif式を使う
```rust

fn main(){

    let condition = true;

    let number = if condition{
        5
    }else{
        6
    };

    println!("number is {}", number);

}

loop!!

fn main(){

    let mut count: i32 = 0;

    loop{

        println!("loop {}", count);

        if count >= 1_000 {
            break;
        }

        count += 1;
    }

}

whileでfor

fn main(){

    let a = [10, 20, 30, 40, 50];
    let mut index = 0;

    while index < 5 {

        println!("value is {}", a[index]);

        index = index + 1;
    }

}

for

fn main(){

    let a = [10, 20, 30, 40, 50];

    for elem in a.iter(){

        println!("value is {}", elem);

    }

}

range関数(start..end)

fn main(){

    for number in (1..4) {
        println!("number is {}", number);
    }

    for number in (1..4).rev() {
        println!("number is {}", number);
    }
}

==
number is 1
number is 2
number is 3

// rev
number is 3
number is 2
number is 1

イエス！