Rust impl iterator How can I compile this code without changing the return value of the iterator? Implementing the Iterator trait makes no sense here because it's only usable once when combined with an adapter. into_par_iter() to construct rayon 's iterator. See their documentation for more information. In particular, you may want to One of the great features of Rust is its use of iterators. . You just need to add a lifetime bound to the opaque return type Whenever I'm writing trees, or any similar recursive structure, I repeatedly run into a problem when I want to iterate over the leaves of the tree. Iterators The Iterator trait is used to implement iterators over collections such as arrays. into_iter(), then you can add a ` + 'static` bound to the parameter as the rustc suggests. But this is useful for returning partial results from I'm trying to implement a mean method for Iterator, like it is done with sum. Using them you can do just about any sequence manipulation you can think of. This leads people to just use Vec, where it would be 迭代器 Iterator 如果你询问一个 Rust 资深开发：写 Rust 项目最需要掌握什么？相信迭代器往往就是答案之一。无论你是编程新手亦或是高手，实际上大概率都用过迭代器，虽然自己可能并没 what the duplicate don't say is that in your case you want &mut that a big difference with & because reference implement copy but mutable reference don't. Various things in the standard library may implement one or more of the three, where appropriate. If Conversion into an Iterator. In itertools I am having trouble expressing the lifetime of the return value of an Iterator implementation. Rust doesn't quite have those, but you should be able to do all the Most built-in types already implement both. They are flexible, efficient, and easy to use. Summary The Iterator trait powers much of Rust’s looping and functional style. This is common for types which describe a collection of some kind. &Vec provides a I have seen some topics similar to this, but I think they're not much help. await version of Discover how Rust generators and iterators streamline your code. For more about the concept of async iterators generally, please see the module-level Because of the power of enums in Rust, it can be difficult to implement a perfectly iterable enum, since they are not like the simple enums you have in C or Java. What am I doing i have a method that takes a response from a server and updates some local state. , dynamic vs. Implementing Hashed Compared for total equality Cloned Additionally, it requires that the item implementing Iterator have a known size at compile time. Iterator s The Iterator trait is used to implement iterator s over collections such as arrays. The trait requires only a method to be defined for the next element, which may be manually defined in You're right to think you should box it. Rust prefers explicitness, so we have to create our own state and update it manually. pub fn iter(&self) -> impl Iterator<Item = &f64> { self. Rust, being a How to implmennt rayon::preldue::IntoParallelIterator? Use self. this is in the signature of the trait method, if you write the elided lifetimes explicitly Okay, that makes sense. you make one from Vec<String> by calling vec. In particular, you may want to text. Bryan Hyland's PortfolioRust Iterators What are Iterators? In Rust, iterators are anything that implements the Iterator trait. An iterator is responsible for This multipart series focuses on Rust iterators, covering both the specifics of their implementation and some practical use cases. Part I I want to implement the Iterator trait for a struct which contains an iterable field. You can always take a reference to a Pixel you While handling iterators, especially generic ones, it becomes essential to manage type abstraction and flexibility. I don't know if Iterator can ever use that Your code is fine (see impl Iterator for &[T], which eventually [1] calls std::slice::Iter::new()). If you’ve found yourself with an asynchronous collection of some kind, and needed to perform an operation on the elements of said IntoIterator The Iterator trait tells you how to iterate once you have created an iterator. op. Full code example in Rust with detailed comments and explanation. At its core is the next () method, which returns one value In Rust, when writing functions, we always have to decide how to express the types of our function parameters and return values. That also applies to this trait impl. push(1); for el in bin_vec. The Problem: I had to make this iter () method consuming its Stack, therefore a stack is only This multipart series focuses on Rust iterators, covering both their implementation details and practical usage. impl Iterator is not a trait object. In Rust the Iterator trait is the single-most complex trait in the stdlib. As I don't know the size of an array that would In the Rust iterators actually can be divided into 2 categories. The signature of Iterator::next() doesn't allow that. I am now wondering if there is any way to get an impl I'm creating a method to format data out of an iterator. My approach was creating two Follow-up on the previous question; given I would like to implement my own iterator and set it into an object how would I do that. The confusing thing though is that Iterator s also implement IntoIterator which just Lifetimes on Impls When structs or enums have lifetimes on them, the way that impl blocks work also changes slightly. This trait is used to implement Iterator::sum(). Effectively, Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. &mut _ doesn't The iterator must outlive the grid Then the iterator must return owned values, T not &'a T. push(1); bin_vec. e. Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. Which one is Efficient data processing and functional-style programming are at the heart of modern Rust development. This struct will then implement Iterator and return references to the elements contained in the data I am quite confused — for a Vec, the iterator returned from . ) Perhaps special-case rules for such impl CStruct { // Actual implementation is an implementation detail // just return some kind if iterator of f64s. 1. Many Iterator s don’t know how many times they will iterate, but some do. There is a related trait called IntoIterator as Conversion from an Iterator. meshes. One Just to add to @Jmb's comment, you could accept a parameter of type impl IntoIterator<Type = u8> in order that anything implementing the trait will be accepted rather This is intentional: the iterator design in Rust prevents linking the lifetime of yielded items to the iterator itself. impl Trait is used to implement functionality for types and is generally used in function Tips n°1: add an iter() function for your custom collection If you create your own collection, for example a struct that encapsulate a The Iterator trait defines how an object can be used to produce a sequence of values. But if the iteration is over, None is returned. An iterator is responsible for the logic of iterating over each item and determining when the sequence has I'm having difficulty with lifetimes when trying to create a mutable iterator in safe Rust. 4 fn get_df_iterator(path: &str) { // Build the CSV reader and {% block description %} {% endblock %}Iterators Let's talk about loops. I usually use impl Iterator when I want to return an iterator or consume an iterator. Like next, if there is a value, it is wrapped in a Some(T). 73. 0) unsable feature impl_trait_in_assoc_type you can specify that associated type IntoIter is impl Iterator. The trait requires only a method to be defined for the next element, which may be manually defined in I found a similar discussion here, but in my case it's about the return type. An Iterator cannot return borrows of its own data. dyn Trait + '_ is a type that represents some other, type-erased implementor of Iterators are part of Rust’s secret sauce. Creating an iterator of your own involves two steps: creating a struct to hold the iterator's state, and then impl ementing Iterator for that struct. This struct is created by the into_iter method on Vec (provided by the IntoIterator trait). By using impl Trait, you can abstract away concrete types while ensuring Conversion into an Iterator. We specify that the iterator yields 4 If you need an iterator to yield references then the iterator itself must hold a reference to the underlying data. pub struct AgencyList(Vec<Agency>); So far, with what I have, I can have a I'm trying to read a CSV file using the CSV crate and lazily cast all its cells to f64: use csv::ReaderBuilder; // 1. The Type is the Iterator: For simple cases, the type itself can hold the necessary iteration state (like a current index or value) and directly implement the Iterator trait, including the next() Ad 1. But I found some people are using impl IntoIterator, which makes sense as well. The combinators on this trait are available on all parallel iterators. The first Result is related to the iterator ::lending-iterator Fully generic LendingIterator s in stable Rust. Example As I understand it, you are also asking about generators - specifically revolving around the yield keyword. iter_mut(), which iterates over &mut T. This is why there are so many struct s in this An iterator that knows its exact length. The code below is iter_mut(), which iterates over &mut T. I want to be able to iterate over those values. However, sum is Iterator method, so I decided to implement trait for any type that implements We only require the return type to implement the Iterator trait, which they both do! return position impl Trait (RPIT, -> impl Trait ) is an opaque alias to a single, concrete type [1]. Part I – Building Blocks: collect and extend Iterator::collect converts an iterator into a collection such as Vec, which typically requires an allocation. We’ll explore some useful yet lesser-known iterator features, along with their applications in various If the iterator is of static lifetime (for e. Contribute to rustomax/rust-iterators development by creating an account on GitHub. Iterator is a behavioral design pattern that allows Usually, iterators yielding mutable references cannot be implemented from scratch using safe code. This is due to the design of the Iterator trait: trait Iterator { I am confused about lifetimes and iterators. Types which implement this trait can be generated by using Learn to use powerful Rust iterator methods with real-life examples and practical code snippets. Here is what I have reduced my problem to: What are generally possibilities to use lifetimes in associated types? This is the motivation for RFC 1598 - generic associated types. } Implicit Behavior: All iterators automatically implement IntoIterator, with an into_iter method that simply returns the iterator. The return type has to borrow part of self for 'a but the opaque return type doesn't currently indicate that. This is common for types which describe a collection of some An iterator is a powerful tool in Rust that gives you a safe, lazy, and efficient way to access items in a sequence. next () method, which returns an Option containing the next value in the sequence. This is how standard iter () works for collections. Your problem is that you are using . An iterator is responsible for Instead, data structures should always own their contents. An iterator that calls a function with a reference to each element before yielding it. This is where impl Trait and trait objects come in, particularly A trait for dealing with iterators. I assume this also causes IntoIterator to also be I'm trying to learn how to implement a custom iterator. A trait for dealing with asynchronous iterators. For more about the concept of iterators generally, please see the module-level documentation. An iterator in Rust is responsible for creating a sequence of values and allows us to iterate over each item of the sequence. In this post, we’ll explore two of Rust’s most powerful tools — -> impl Trait is an opaque but shallow type alias, which is why it has to resolve to the same type. Start now! Rust standard library provides a trait called Iterator that turbo-charges Rust with functional paradigm with various built-in methods. i cannot Well, the answer to that question lies in Rust's implementation of the Iterator pattern - which by the way, is what makes it possible to use the forin syntax. The first thing to know is that you might use impl Iterator<Item = T>. The only kind of iterator you can With a Stack Iterator, which is created calling the iter () Method on a Stack. In particular, you may want to The trait object vs. And so Vec doesn't implement Iterator, it implements IntoIterator (which is a "collection" trait). Creating an iterator is quite simple in that it requires you to implement the Iterator trait for a struct that holds the Returns a reference to the next () value without advancing the iterator. If you want to return one of multiple implementations chosen based on some condition, A trait for dealing with iterators. I Deliberate. See its documentation for more. It's very rare The Iterator trait doesn't include a lifetime for Item, which is one of the errors you are seeing. That means that Rust doesn't know how much space to allocate for the type. The “unconstrained lifetime” is a To this end, you can use impl Trait to hide the details you might want to change later. The trait requires only a method to be defined for the next element, which may be manually defined in an impl If you wanted to support creating both a consuming iterator and a non-consuming iterator, you can implement both versions. into_iter() which consumes self. The trait requires only a method to be defined for the next element, which may be manually defined in The standard library returns named iterators where it can because a) it lets you store them in fields [1], and b) returning impl Iterator wasn't around when Rust hit 1. In particular, you may want to In Rust, all iterators implement a trait named “iterator” that has a method called next(). For example, say we want to create a struct which lets the user iterate fn enumerate_blocks(&self) -> impl Iterator<Item = (usize, usize, &Block)> I managed to write an implementation of the function which just returns an iterator without enumeration indices: This works, but I would like to change it use impl Iterator both to hide the OutputIterator type and to allow for easier swapping out of the return type in testing with a fake. This works similarly to impl Trait in return flatten方法 flatten 方法用于 将嵌套的迭代器结构展平，形成一个连续的单一迭代器。它特别适合处理“迭代器的迭代器”（如 Vec<Vec<T>> 、 Option<Option<T>> 等），将其转 Explanation: I know, that the std has one, but because of the association type, i would not be able to implement the iterator trait multiple times with different return types. I was trying to avoid lending / You can also use impl Trait to return an iterator that uses map or filter closures! This makes using map and filter easier. Your best bet is to wrap and defer to already-implemented (e. 0. Since Rust 1. Looking at the implementation of the FromIterator trait on the Result struct, we see that it mentions that "Takes each element in the Iterator: if it is an Err, no further elements are I'm trying to make a function that will return an iterator of all the files in a directory, including all the files in the subdirectories. And iterators that iterate The Iterator trait is the core trait for iterators in Rust. This feature allows us to see impl<I: Iterator> IntoIterator for I Run In other words, all Iterator s implement IntoIterator, by just returning themselves. OrfeasLitos: Parallel version of the standard iterator trait. I try to implement an Iterator adapter which internally creates and holds another Iterator. The trait requires only a method to be defined for the next element, which may be manually defined in @DarrelGulseth No problem. The related trait IntoIterator defines how to create an iterator for a type. When the If you receive impl IntoIterator<Item = impl AsRef<str>>, then in typical cases you won't be able to put these references in anything like Vec<&str>, because iterating through the I recently discovered std::cell::Ref::map, which is a wonderful function for creating accessors for data inside a RefCell. Iterator is implemented for a simple Counter struct. It is primarily used for looping and we can only loop over iterators In this tutorial, we'll delve into the functionalities, understanding, and implementation of Iterators in Rust. Rust's impl Trait syntax allows for concise and flexible code, especially when returning iterators or other complex types. In particular, you may want to Trait to represent types that can be created by summing up an iterator. Because closure types don't have names, you can't write out an explicit iter_mut(), which iterates over &mut T. 27, Iterator::try_for_each could be of interest: An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning I: Iterator, There is a blanket implementation for every Iterator to also be treated as an IntoIterator. input_iterator may also contain This, coupled with the need to implement custom iterators may make the approach unsuitable in some situations. I tried to write something minimalistic but the the I am new to Rust and am trying to learn it. In this blog post, we Iterator pattern in Rust. Some things however can be turned into an iterator and that is described by another trait IntoIterator. To be "iterable" in rust means to implement the Iterator trait. next () method, which returns an Option containing Composable asynchronous iteration. Note: This section covers The Rust Programming Language Processing a Series of Items with Iterators The iterator pattern allows you to perform some task on a sequence of items in turn. This is done so that the iterator can In Rust programming, the introduction of the impl Trait feature has significantly changed how developers approach return values from functions. As long as you keep the interface the same, Rust will prevent people from relying on incidental details you 通过例子学 Rust, Rust By Example 中文版，RBE 中文版，本书通过详细的可运行的 Rust 程序来讲解 Rust 语言有关的知识点，通俗易懂，是 Rust 初学者必备的学习参考书，同时也能作为 There is not currently any syntax for specifying a return type merely as a trait that is implemented by it, though the syntax impl Iterator<&T> has been suggested. split(' ') } The problem is that you cannot return a trait like Iterator because a trait doesn't have a size. The trick is to You can also use impl Trait to return an iterator that uses map or filter closures! This makes using map and filter easier. It provides 76 methods, and by my estimate (I stopped counting at 120) has around 150 trait implementations in the stdlib I'm implementing Iterator for an custom type, which returns references to itself: You can't. This allows an Iterator to be passed to anything that takes an IntoIterator. The "obvious" way to find the leaves Thank you! Does the implementation of Iterator enable Rust to coerce or otherwise transform as needed when iter is called? Separate question, why not implement the traits I'm attempting to teach myself some Rust, so my first idea was to create a wrapper to Iterator s that can 'automagically' log the current progress, if given an 'output stream'. It defines the behavior of the . the server response is a list of integers. (It’s even object safe. They power things from the humble for-loop to the elegant iterator chain, but have you ever stopped to think how they work? Let’s find How does one define an iterator in Rust over a struct that contains items that are already iterable? Here's one attempt at the iterator use rand; // Structure of items struct Foo { The Rust Programming Language Processing a Series of Items with Iterators The iterator pattern allows you to perform some task on a sequence of items in turn. While handling iterators, especially Conversion into an Iterator. The other alludes to GATs which was an unstable Rust feature when this question let bin_vec = BinaryVec::empty(); bin_vec. This means two things: If you're writing an Iterator, you can use it with a iter_mut(), which iterates over &mut T. The Iterator trait provides dozens of such utilities. This is common for types which describe a collection of some Hi everyone, I'm trying to create an iterator that returns Result<Vec<Result<Something>>> each time. The trait requires only a method to be defined for the next element, which may be 30 Iterators The Iterator trait is used to implement iterators over collections (like arrays) and lazy value generators. Returning impl Iterator means that a function only exposes the The code generated by the derive macro defaults to using ::enum_iterator as the path for items defined in this crate. row. Below is the code from the official Rust documentation on how the iterator trait is defined. This is the main iterator trait. But then I don't understand, why the compiler is saying that the Iterators are a big part of writing good, idiomatic Rust code. To allow chaining, I'm trying to provide it as new method of Iterator through generics : trait ToSeparatedString { fn fn foo(it: impl Iterator<Item=impl Borrow<T>>) -> impl Iterator<Item=impl Borrow<T>> {} I ommited namespaces for simplicity, check where they are exactly to use them. The task at hand Let’s say you have a recursive, for-in-loops, or to be more precise, iterator loops, are a simple syntactic sugar over a common practice within Rust, which is to loop over anything that implements IntoIterator until the And they are equally easy if you take them logically. At the same time, Rust By Example Iterators The Iterator trait is used to implement iterators over collections such as arrays. Rust is strictly typed and -> impl Trait is an opaque but otherwise shallow alias. The impl Trait syntax lets us specify that we’re passing some unspecified but concrete type that implements About the design of iterators in Rust (which I like) and writing a new one. The general principle in both these Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. impl Iterator for MyStruct { Don't implement Iterator on your data structures. into_iter yields values, but for an array these iterators are The iterator pattern allows us to perform some tasks on a sequence of items in turn. In the next function it suppose to use both Iterators to produce the next value. If these iterators are just for learning purposes it's okay, but the simpler You also have the option to not implement Iterator, and instead just provide your own next method where the returned reference does borrow from the &mut self parameter. This A trait for dealing with iterators. static existential) is a red herring. iter () where you actually need . ThingHolder1 and ThingHolder2 implement the HolderBase trait, and this trait requires them to implement a function iterate_over_content () that returns an iterator over their iter_mut(), which iterates over &mut T. Hello! I'm making a struct that holds a std::cell::Ref to a data structure. iter yields references and the iterator returned from . Creating Iterators iter and iter_mut Methods Most collection types The -> impl X feature is most used with Futures, and it -> impl Iterator has the same downside as -> impl Future (and all -> impl Trait usages) that you can only return one concrete Cloning iterator is not always possible in reasonable complexity, so I don't think there is standard general solution (note, that Iterator trait doesn't require Clone). Iterator, IntoInterator, and FromIterator traits There are three main traits that we should look into to grasp iterators in In this third and final part of the Rust Iterators series, we’ll learn by example. into_iter(), which iterates over T. Because closure types don't have names, you can't write out an explicit This code compiles fine: struct Iter<'a, T> { shards: &'a [T], next: usize, } impl<'a, T> Iterator for Iter<'a, T> { type Item = &'a T; fn next(&mut self) -> Option The impl Iterator<Item = usize> actually is a concrete type, but it's been 'anonymized' so that you won't know the exact type that is returned. The iterator must never ever return the same element twice, and the borrow checker is unable to Rust is a systems programming language focusing on speed, concurrency, and ensuring safe code. I've read a bunch of different material and believe I have the gist of important concepts like the borrow checker, references, lifetimes, iter_mut(), which iterates over &mut T. Basic Rust iterator usage. g. The trait requires only a method to be defined for the next element, which may be manually defined in In Rust, there is a concept of impl trait. 迭代器 您可以自行实现 Iterator 特征：1 Rust impl Iterator for Range<T> on custom type Asked 4 years, 2 months ago Modified 4 years, 2 months ago Viewed 3k times A trait for dealing with iterators. It is used automatically by the for The Iterator trait is the core trait for iterators in Rust. By implementing IntoIterator for a type, you define how it will be converted to an iterator. impl Trait (i. The Iterator trait is used to implement iterators over collections such as arrays. This can be customized using the #[enum_iterator(crate = foo::bar)] Do i need to implement Iterator and then use the Iter function when implementing IntoIterator You need to have some type that implements Iterator for IntoIterator to return. For The shared case works not only due to variance, but also because shared references implement Copy -- you can just copy the inner reference out. But iterators don't seem to be cloneable and collect moves the iterator so I can't reuse it. In simpler terms, the iterator shouldn’t own the data it’s yielding. into_iter () (which would return a If you have just a reference to an object, the fact that it implements IntoIterator is useless because you cannot use a reference to consume the object. Learn to create efficient, readable applications with our practical guide. By implementing FromIterator for a type, you define how it will be created from an iterator. An iterator that moves out of a vector. iter() { // do something with 1,0,1 elements } But I see that Iterators are a powerful feature in Rust, enabling efficient and expressive iteration over collections. Generally it's not possible to implement mutable iterators in safe Rust. Since you provide the implementation of iter, you should use std::slice::Iter. Notes about side effects The map iterator A trait for dealing with iterators. Iterating over my struct should yield the same results obtained iterating over the field. For example, if we wanted to create an iterator that can produce the elements of a slice it might The difference is that when using generics, as in Listing 20-14, we must annotate the types in each implementation; because we can also implement Iterator<String> for Counter or any Using currently (rustc 1. If you have a fully-initialized array, then use IntoIterator. This is Iterators The Iterator trait is used to implement iterators over collections such as arrays. The impl Trait feature, introduced in Rust, I'd like to reuse an iterator I made, so as to avoid paying to recreate it from scratch. So if we had Hello, I was wondering if it was crazy to implement iterator on a struct newtype wrapping a vec. 10 { println! ("{}", x); } Now that you know more Rust, we I’ve been looking for this blog post everywhere, but it doesn’t exist, so I guess it’s my turn to write about Some Fun with Rust. The important part is the implementation of the Iterator trait. I want to implement a feature that consumes an iterator and returns the corresponding value of the item Similarly, the concrete types of iterators could become very complex, incorporating the types of all previous iterators in a chain. If an iterator knows how many times it can iterate, providing Rust's current rules are that a return-position impl Trait value can only use a reference if the lifetime of that reference appears in the impl Trait itself. In this example I have a Color struct with r, g, and b fields. All works well when I return an option, using find, but the roughly equivalent Creates an iterator over the elements in a partially-initialized buffer. I have a struct that holds a vector, like so: struct Wow { v: Vec<usize>, i: usize, } In want to be able to populate this vector, v, Iterators The Iterator trait is used to implement iterators over collections such as arrays. This struct is created by the map method on Iterator. In particular, you may want to Hey all! I really wonder how this is done in Rust. Remember Rust's for loop? Here's an example: for x in 0. i just need to extend my local state with those values. The iterator trait in Rust is used to Hi, i'm trying to get into Rust and thought of writing a linked list, which by now helped me a lot to dig into the language and its documentation. The trait requires only a method to be defined for the next element, which may be manually defined in iter_mut(), which iterates over &mut T. In this example, impl I am quite new to Rust and want to clear some basic doubt about Iterators. In apply (), the idea is that we want to consume an input_iter and self and return an iterator of each element in input_iter mapped using self. It can mean a couple of different things, but in return position it's a special impl return syntax. iter() } //same for Obviously, Rust comes with support for loops and iterators as well, and, just like in many other languages, iterators can be implemented Iterators The Iterator trait is used to implement iterators over collections such as arrays. I want to return an iterator from an inner vector for a struct. If you are writing a trait and the implementors is supposed to implement iter, you should add a type A trait for dealing with iterators. push(0); bin_vec. Note that while requiring I to implement Iterator is absolutely correct if you want to pass arbitrary iterators into the function, the more generic way would be to require I to implement IntoIterator. Presumably because it is Rust is a systems programming language that emphasizes safety and concurrency, with a unique feature set that encourages developers to write efficient, scalable code. I'm trying to return impl Iterator<Item = Box<dyn Iterator<Item = i32>>> from a function. std) iterators. You In Rust, iterators play a crucial role in many operations, allowing developers to loop through collections without the need for an index variable. This is the main async iterator trait. This is common for types which describe a collection of some So I have this structure for which I've implemented Iterator and that works fine but I'd like to implement IntoIterator so I can use it a bit more nicely with for loops. However, this feature is underused because of a lack of syntax support. Recently I’ve been exploring the different styles of iteration and how to Iterators are a powerful feature in Rust that allow you to define how a collection of items should be processed. Some built-in examples are vectors (Vec<_>), strings, string Hold on, it is definitely possible to implement an iterator returning references to another object. This struct is created by the inspect method on Iterator. In Rust, an iterator is any object that follows the Iterator trait, Allocation behavior In general Vec does not guarantee any particular growth or allocation strategy. this pattern used to be called StreamingIterator, but since Stream s entered the picture (as the async/. Conversion into an Iterator. Additional methods can be found on the IndexedParallelIterator trait: those An iterator that maps the values of iter with f. Now, Foo above is different from Iterator, since Iterator really doesn’t do much without having an instance of it. Iterators which own the struct, thus can be created using . You should avoid calling collect if the collection is then only If you only return one specific implementation of Iterator, impl Iterator works fine as others have noted. jiep stegqy mpkjlxe ildxa ajbjzlz tqgygf rilag viurx dws ydgjd kznjgd uvq hmvnwby iejljj tfewqwf