On the hello world example for Actix: https://actix.rs/
There is a || operator in the new call. I am having a hard time understanding what this is for since there are no operands on the left hand side.
#[actix_web::main] async fn main() -> std::io::Result<()> { HttpServer::new(|| { App::new() .route("/", web::get().to(greet)) .route("/{name}", web::get().to(greet)) }) .bind("127.0.0.1:8080")? .run() .await }