Rust Book Day 1

Question 1

How to quickly verify if compiling is good?

Answer 1

cargo check

Question 2

how to compile it with optimizations?

Answer 2

cargo build –release

Question 3

what is part of the cargo.toml

Answer 3

[package]
name = “hello_project”
version = “0.1.0”
edition = “2020”

Comment
[dependencies]
list your crates here

Question 4

Print hello world

Answer 4

fn main() {
println!(“hello world”);
}

Question 5

how to compile and run straight away?

Answer 5

cargo run

Question 6

how to build and then execute separately?

Answer 6

cargo build
then execute
./target/debug/project_name

Question 7

How to ask for command line input (like a guess)

Answer 7

io::stdin()
.read_line(&mut guess)
.expect(“Failed to read line”);

Question 8

How to import standard input library for terminal inputs?

Answer 8

use stdin::io;

Question 9

How to create a variable whcih is a mutable string

Answer 9

let mut my_variable = String::new();

Question 10

when using read_line(&mut guess) we are passing the variable guess. why must it be mutable?

Answer 10

Because we are appending stuff to the string as we are writing it seems, growing the string

Question 11

what does the & in &mut guess indicate?

Answer 11

that this argument is a reference, no need to copy the data into memory multiple times

references are also immutable by default, so you need to write &mut here

Question 12

read_line() returns a Result which is an …

Answer 12

enum

it is a type that can be in one of multipel possible states (each possibile state is called a variant)

Question 13

what is Rng in use rand::Rng;

Answer 13

a trait

it defines methods, so the trait must be in scope for us to use those methods

Question 14

turn string into integer

Answer 14

let guess: u32 = guess.trim().parse().expect(“should be a number”);