The Rust Prelude at
std::prelude is the list of things automatically imported by Rust.
For other things, we have to use the syntax
use std::io;The String type has the new associated function that can be used via the ::
syntax
let mut guess = String::new();This is similar to what other languages call static methods. ::new() returns an
instance of the type, in this case String.
Some methods return a value of type Result. In our case, read_line returns an
io::Result (which is itself a specialization of the generic Result).
These are enumerations whose variants are Ok or Err.
The expect
method can be called on these Result values to either return the usable value if it
resulted in Ok, or crash and take some action if it's an Err.
One very nice feature is that if you forget to handle the Err case, you'll get a
warning.
You can go to Crates.io and search for the Crate you want. They
include what to copy to your Cargo.toml file.
As of this writing, there's no built-in command line way of doing this operation without editing the file, but there's third-party Cargo subcommands that do this.
There's petitions to add this functionality to Cargo proper though, so it's possible they add it at some point.