For now, you have to use the “long” form: v.sort_by(|x, y| key(x).cmp(&key(y))); Why am I getting these errors? Is there any way to fix them? The cause and fix are one-and-the same: Rust is simply not currently expressive enough to represent what you want. The feature needed is called generic associated types (GATs); previously known … Read more
Lifetime ‘a in fn foo(&’a self, …) … is defined for impl<‘a>, that is it is the same for all foo calls. Lifetime ‘a in fn get_mut<‘a>(&’a mut self) … is defined for the function. Different calls of get_mut can have different values for ‘a. Your code impl<‘a> Foo<‘a> { fn foo(&’a self, path: &str) … Read more
According to the C++03 standard, a temporary bound to a reference has differing lifetimes depending on the context. In your example, I think the highlighted portion below applies (12.2/5 “Temporary objects”): The temporary to which the reference is bound or the temporary that is the complete object to a subobject of which the temporary is … Read more
Lifetime elision infers that the full type of fn get_str(s: &str) -> &str is fn get_str<‘a>(s: &’a str) -> &’a str which basically means that the return value of get_str has to be valid as long as s is valid. The actual type of the string literal “Hello world” is &’static str, which means that … Read more
c99 support variable length arrays but c90 does not support variable length arrays, you can see this more clearly if you are using gcc and try to compile with these arguments: gcc -std=c89 -pedantic this will give you the following warning: warning: ISO C90 forbids variable length array ‘y’ [-Wvla] but if you compile using … Read more
There are a two solutions to your problem. Let’s start with the simplest one: Add a lifetime to your trait trait Foo<‘a> { type Item: AsRef<Path>; type Iter: Iterator<Item = Self::Item>; fn get(&’a self) -> Self::Iter; } This requires you to annotate the lifetime everywhere you use the trait. When you implement the trait, you … Read more
The sessions on PHP works with a Cookie type session, while on server-side the session information is constantly deleted. For set the time life in php, you can use the function session_set_cookie_params, before the session_start: session_set_cookie_params(3600,”/”); session_start(); For ex, 3600 seconds is one hour, for 2 hours 3600*2 = 7200. But it is session cookie, … Read more
Despite your best intentions, your hint function may not have the effect you expect. But we have quite a bit of ground to cover before we can understand what’s going on. Let’s begin with this: fn ensure_equal<‘z>(a: &’z (), b: &’z ()) {} fn main() { let a = (); let b = (); ensure_equal(&a, … Read more
Here’s a minimal reproduction: #[derive(Debug)] pub struct Canvas; impl Canvas { fn new() -> Self { Canvas } fn color(&self) -> &Canvas { self } } fn main() { let mut canvas = Canvas::new().color(); // 1 ^~~~~~~~~~~~~ // 2 ^~~~~ println!(“{:?}”, canvas); } Rust 2015 error[E0597]: borrowed value does not live long enough –> src/main.rs:15:22 … Read more
The C++ Standard does not say where string literals should be stored. It does however guarantee that their lifetime is the lifetime of the program. Your code is therefore valid.