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Philipp Flenker committed Mar 31, 2024
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7 changes: 6 additions & 1 deletion src/main.rs
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@@ -1,3 +1,8 @@
use std::io::{self, Read};

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pflenker Mar 31, 2024 •
edited

Owner

In layman's terms, this line tells rust: "From the Standard Library ( std), I want to use Input and Output stuff (io)".
This line is a shorthand for:

use std::io;
use std::io::Read;

We will use io below, but we won't use Read, so why import it here?
In short, it's a Trait, something we will revisit a bit later.
In a nutshell, Read brings the implementation for bytes with it. Try removing it and see what happens.

fn main() {
println!("Hello, world!");
for b in io::stdin().bytes() {

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pflenker Mar 31, 2024

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What this line does is can be stated as: "For every byte you can read from the keyboard, bind it to b and execute the following block".
This is what the individual pieces do:

  • io represents Input/Output, we imported this above.
  • ::stdin() calls the function stdin() on io, which represents the Standard Input.

Calling bytes() on io::stdin() returns something we can iterate over, or
in other words: Something which lets us perform the same task on a series of
elements. In Rust, same as many other languages, this concept is called an
Iterator.

Using an Iterator allows us to build a loop with for..in. With for..in in combination with bytes(), we are asking rust to read byte from the standard input into the variable b, and to keep doing it until there are no more bytes
to read. More on that in a second back in the tutorial text.
let c = b.unwrap() as char;
println!("{}", c);

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pflenker Mar 31, 2024

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These two lines basically print out the character that was read - we'll describe this more thoroughly in a bit (and I promise, I'll explain unwrap and println! in due time!)
}
}

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