rust

问题 I have spawned a child process using Rust's Command API. Now, I need to watch this process for a few seconds before moving on because the process may die early. On success, it should run "forever", so I can't just wait. There's a nightly feature called try_wait which does what I want, but I really don't think I should run Rust nightly just for this! I think I could start a new thread and keep it waiting forever or until the process dies... but I would like to not hang my process with that

问题 I want to pass Iterators to a function, which then computes some value from these iterators. I am not sure how a robust signature to such a function would look like. Lets say I want to iterate f64. You can find the code in the playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=c614429c541f337adb102c14518cf39e My first attempt was fn dot(a : impl std::iter::Iterator<Item = f64>,b : impl std::iter::Iterator<Item = f64>) -> f64 { a.zip(b).map(|(x,y)| x*y).sum() }

问题 Given this code: trait Base { fn a(&self); fn b(&self); fn c(&self); fn d(&self); } trait Derived : Base { fn e(&self); fn f(&self); fn g(&self); } struct S; impl Derived for S { fn e(&self) {} fn f(&self) {} fn g(&self) {} } impl Base for S { fn a(&self) {} fn b(&self) {} fn c(&self) {} fn d(&self) {} } Unfortunately, I cannot cast &Derived to &Base : fn example(v: &Derived) { v as &Base; } error[E0605]: non-primitive cast: `&Derived` as `&Base` --> src/main.rs:30:5 | 30 | v as &Base; | ^^^^

问题 This question already has an answer here : Why does the compiler not complain that an iterator moved to a for loop is immutable? (1 answer) Closed 15 days ago . In stdlib string.rs: impl Add<&str> for String { type Output = String; #[inline] fn add(mut self, other: &str) -> String { self.push_str(other); self } } let s1 = String::from("tic"); let s2 = String::from("tac"); let s = s1 + &s2;// it works s1 is immutable here, but Add::add( mut self , other: &str) is mut, I just want to know why.

问题 Given the implementation below, where essentially I have some collection of items that can be looked up via either a i32 id field or a string field. To be able to use either interchangeably, a trait "IntoKey" is used, and a match dispatches to the appropriate lookup map; this all works fine for my definition of get within the MapCollection impl: use std::collections::HashMap; use std::ops::Index; enum Key<'a> { I32Key(&'a i32), StringKey(&'a String), } trait IntoKey<'a> { fn into_key(&'a self

问题 I'm trying to implement a collection that stores values in both a vector and a hashmap and this is what I have so far: pub struct CollectionWrapper { items: Vec<Item>, items_map: HashMap<ItemKey, Item>, } impl CollectionWrapper { pub fn new() -> Self { CollectionWrapper { items: Vec::new(), items_map: HashMap::new(), } } pub fn add(&mut self, item: Item) { let key = item.get_key(); self.items.push(item.clone()); self.items_map.insert(key, item.clone()); } } I obviously need some kind of lock.

问题 I'm trying to implement a collection that stores values in both a vector and a hashmap and this is what I have so far: pub struct CollectionWrapper { items: Vec<Item>, items_map: HashMap<ItemKey, Item>, } impl CollectionWrapper { pub fn new() -> Self { CollectionWrapper { items: Vec::new(), items_map: HashMap::new(), } } pub fn add(&mut self, item: Item) { let key = item.get_key(); self.items.push(item.clone()); self.items_map.insert(key, item.clone()); } } I obviously need some kind of lock.

问题 I'm building a service that periodically makes an HTTP request. I'm using tokio::timer::Delay as a periodic trigger and hyper to make the HTTP call. Using them together gives me the following error: thread 'tokio-runtime-worker-1' panicked at 'cannot recursively call into `Core`', libcore/option.rs:960:5 How can I make this work? Below is a simplified version of the service. main.rs extern crate futures; extern crate hyper; extern crate tokio; extern crate tokio_core; extern crate tokio_timer

问题 I'm struggling to turn a simple recursive function into a simple iterator. The problem is that the recursive function maintains state in its local variables and call stack -- and to turn this into a rust iterator means basically externalizing all the function state into mutable properties on some custom iterator struct. It's quite a messy endeavor. In a language like javascript or python, yield comes to the rescue. Are there any techniques in Rust to help manage this complexity? Simple

问题 I'm struggling to turn a simple recursive function into a simple iterator. The problem is that the recursive function maintains state in its local variables and call stack -- and to turn this into a rust iterator means basically externalizing all the function state into mutable properties on some custom iterator struct. It's quite a messy endeavor. In a language like javascript or python, yield comes to the rescue. Are there any techniques in Rust to help manage this complexity? Simple