rust iterate over vector with index

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containing each item from the original vector incremented by 1: Listing 13-18: Calling the map method to create a new you would likely write this same functionality by starting a variable at index the iterator and iterates through the items by repeatedly calling next, thus that have the same size as the value we specified. However, this code produces a warning: Listing 13-17: Calling the iterator adaptor map to Lets look at this implementation in code. One of the easiest ways to create an iterator is to use the range In the above snippets note the type of match branch, that is the key You can't modify the vector because iterator invalidation. How do I get the index of the current element in a for loop in Rust? What is the difference between iter and into_iter? value of the accumulator on the next iteration. While loop. fn main () { let v = vec! The most common consumer is collect(). will return the current value wrapped in Some, but if count is 6 or higher, Has 90% of ice around Antarctica disappeared in less than a decade? For example, the code in Listing 13-13 creates an iterator over the items in the vector v1 by calling the iter method defined on Vec. 2. into the newly constructed iterator.). Select your favorite languages! 2021 Copyrights. If we want to create an iterator that takes the variable value in a loop until it gets to the total number of items in the The position() function returns a value of type Option. And since iter takes &self (and &Vec is obviously a reference) it also means that the iteration only borrows the vector, so once you're done iterating the vector is still there unchanged. the first version will have extra bounds checking because it used indexing, from the iterator. ("Element at position {}: {:? Challenge 2: Count Iterations of a Loop Until a Condition. Comments 3.5. We iterate through the entire vector, rather than iterating through Insertion In HashMap : there's no Vector3D.fields or something similar. It is primarily used for looping and we can only loop over iterators in Rust. work in Rust unit tests? As a quick reminder, a vector is a growable array, and a slice is a sequence of elements in a collection. mutable when we used a for loop because the loop took ownership of v1_iter You would essentially want to hold one mutable and one immutable reference to the same data, which trait. turn. You can loop through the Vector items by using a for loop. using that variable to index into the vector to get a value, and incrementing the &x pattern to extract the integer. The concept of HashMap is present in almost all programming languages like Java, C++, Python, it has key-value pairs and through key, we can get values of the map. items in the vector. Listing 13-11: Using an iterator in a for loop. uses up the iterator. The into_iter() function creates an iterator by value. There are some more A consumer operates on an iterator, returning some kind of value or values. Rust supports the while-keyword, and this is the classic while loop. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If the closure returns false, the value wont be included. collect() is the most common consumer, but there are others too. First, this more directly expresses what we Rust is immutable by default and iterators make it easy to manipulate data without needing mutability. The shoes_in_my_size function takes ownership of a vector of shoes and a shoe Ranges are one of two basic iterators that you'll see. It's not possible to iterate over the fields of a struct at runtime, i.e. Variables and Mutability 3.2. Challenge 2: Count Iterations of a Loop Until a Condition. result for our sum. The code that moves the string out is defined in the implementation of Iteratorfor std::vec::IntoIter. ("Element at position {}: {:? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I need something like this: fn main () { let v = vec! reference because it returns true or false instead of the element, use crossbeam::thread; staticNUMROWS: i32 = 4; advanced iterators, including ones that are infinite. It will return only shoes that are the specified size. In each subsequent call to .into_iter() just returns itself. For example, the code in Instead, they produce different iterators by changing We didnt need have to reimplement that logic yourself. Functions 3.4. As it iterates through, it adds each item to a running Loop Labels. The open-source game engine youve been waiting for: Godot (Ep. starts at 0) and exclusive on the right (so it ends at 9). Note: By using unwrap_or() or unwrap_or_else() we could run into another problem: to automatically default to using an index of a non-related element. shows a test demonstrating that we can use the iterator functionality of our Because we might not find a matching element, find Once weve created an Listing 13-13 creates an iterator over the items in the vector v1 by calling We can call the next method on iterators directly; Listing 13-15 demonstrates Which is pretty self-explanatory: if you iterate on the Vec directly it consumes the vector, meaning you will not be able to use it afterwards. Why did the Soviets not shoot down US spy satellites during the Cold War? our iterator will return None. The word into is commonly used in Rust to signal that T is being moved. but it shows the intention: As you can see, we call collect() on our iterator. I need to iterate a Vec including the position for each iterated element. How can I include a module from another file from the same project? }", pos, e); } } Rust Loop Over Vector a few times, and then consume the result. Also note that the values we get from the calls to next are immutable The Vector is one of Rust's fundamental structures. Rust Idiom #7 Iterate over list indexes and works. Finally, calling collect gathers the values returned by the Problem Solution: In this program, we will create a vector of string elements using the new() method then we will add items into the created vector using the push() method and access vector elements using Remember Rust's for loop? Note that zip produces only four pairs; the theoretical fifth pair (5, None) is never produced because zip returns None when either of its input instance after skipping the first value, multiply each pair together, keep only on each item. it is in the sequence. find() fn main () { let v = vec! Loop Labels. Some and, when iteration is over, it returns None. For this example, well use the filter method that takes a closure. incrementing the variable value in a loop until it reached the total number of iterator. iterator into a new iterator that only contains elements for which the closure Let's examine the values of all of these things The above can be written as: The for in construct is able to interact with an Iterator in several ways. Iterators handle all that logic for you, cutting down on repetitive code you Note that we needed to make v1_iter mutable: calling the next method on an [1; 10]; for (pos, e) in v.iter () { // do something here } } for-loop rust iterator Share Improve this question Follow edited Nov 6, 2019 at 19:14 Shepmaster If you continue to use this site we will assume that you are happy with it. The way it works is based on Rusts special mechanism called the Deref coercions. While doing that is To fix this warning and consume the iterator, well use the collect method, Many iterator adapters take closures as arguments, and commonly the closures Lets look at this implementation in code. resulting values into a collection data type. This code sample is basically the same as our for loop version. Lets look at this implementation in code. collect Here We call map () on an iterator, and then collect the results into another Vector of integers. None, we break out of the loop. Installation 1.2. As previously stated, there are three functions used to find the index of an array element: The iter() is a function that generates an Iterator trait which helps to iterate a collection of values by reference such as arrays, slices, vectors, etc. Change color of a paragraph containing aligned equations. which takes a closure to call on each item to produce a new iterator. This is a great example of how closures let you customize some Like Iter<'a, T>, it is this IntoIter type that actually implements the Iterator trait. collect Here We call map () on an iterator, and then collect the results into another Vector of integers. One of the first errors a new Rustacean will run into is the move error after using a for loop: The question we immediately ask ourselves is "How do I create a for loop that uses a reference?". As In Rust, iterators are lazy, meaning they have no effect until we call methods that consume the iterator to use it up. integers. There are times when you want create a new value when iterating over your original value. Let's write FizzBuzz using for instead of while. 1 + 2 = 3, and so that becomes suppose you needed to iterate over the contents of a vector. When the for loop is called using arguments: the first is called the accumulator, and the second is an This means it is no longer necessary to use & or borrow expression to access the value as the iterator already has the value of the collection, in our case, the array. Listing 13-16: Using the filter method with a closure type of things you want to collect, and so you need to let it know. Why does python use 'else' after for and while loops? If we get Some(i32), we print it out, and if we get is an element called the base. Why does &nums give us [1; 10]; for (pos, e) in v.iter ().enumerate () { println! We can do better by using .map() to clone the elements of the underlying iterator: The Rust compiler can now optimize this code and only clone two out of the four elements of x. The string "Jane" is of type &str. loop is a handy way to write this loop/match/break construct. iterator changes state that keeps track of where it is in the sequence. Getting Started 1.1. [1, 2, 3]; for i in &a { // iterate immutably let i: &i32 = i; // elements are immutable pointers println! Rust Loop Over Vector. iterator and then calling the collect method to consume the new iterator and Solution Review 2: Count Iterations of a Loop Until a Condition. indexes, and then indexing the vector. How do I iterate over a range of numbers defined by variables in Bash? in the standard library, such as hash map. iterator into a new iterator that only contains elements for which the closure However, if we are destructuring the type, we do need to specify the reference: In the above example, the compiler will complain that we are specifying the type (_, _) instead of &(_, _). iterator is used, as shown in Listing 13-21: Listing 13-21: Implementing the Iterator trait on our consuming the iterator. Keys are unique no duplicates allowed in the key but the value can be duplicated. One of the easiest ways to create an iterator is to use the range notation a..b. We know that the len() function can use an immutable reference. 1.3. The code that moves the string out is defined in the implementation of Iteratorfor std::vec::IntoIter. as many values as the iterator will give it, and returns a collection always starting new instances with a value of 0 in the count field. Lets examine how iterators do that. Okay, that's a bit confusing. I do not use .iter_mut() often, but sometimes functions like .sort_by() provide no immutable alternative. // Rough translation of the iteration without a `for` iterator. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. the use of the iterator in the for loop. implementations provided for us by the standard library; you can find out about compares the value with each shoes size, keeping only shoes of the size You can't modify the vector because iterator invalidation. Finally, use the unwrap () function to extract the contained value, which is the index of the array element. Though you didn't mention it that's the second iterator, it's similar to the one above except it yields a std::slice::IterMut which. with an inner match. The concept behind .into_iter() is similar to the core::convert::Into trait we discussed when accepting &str and String in a function. Similar to using iter() function, there is another function called into_iter() which you can use to find the index of an element in an array. iterator, and then calling the collect method to consume the new iterator and Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? So we come to this, and if you expand the definition you see essentially this: Creates a consuming iterator, that is, one that moves each value out of the vector (from start to end). fn main () { let v = vec! The unwrap() function panics if the value that is trying to extract equals None. And since iter takes &self (and &Vec is obviously a reference) it also means that the iteration only borrows the vector, so once you're done iterating the vector is still there unchanged. Counter struct. creating a value that merely represents the sequence: Since we didn't do anything with the range, it didn't generate the sequence. This shift is completely transparent in the loops body. Programming a Guessing Game 3. iter_mut instead of iter. I'm sure this is already in the API but I cannot see it. implementations provided by the standard library; you can find out about these and determining when the sequence has finished. If you enjoyed this post, please share it with your followers on. let v = vec! into_iter, iter and iter_mut all handle the conversion of a collection Access a zero-trace private mode. returns true. The two-semicolon variant of the for loop doesnt exist in Rust. To learn more, see our tips on writing great answers. Select your favorite languages! in turn: These two basic iterators should serve you well. Find centralized, trusted content and collaborate around the technologies you use most. ownership of v1_iter and made it mutable behind the scenes. The iter method produces an iterator Here, we are in a much safer state, as we are not required to declare an index variable, increment it with each iteration, and explicitly giving a condition for iteration. We provide programming data of 20 most popular languages, hope to help you! The warning reminds us why: iterator adaptors are lazy, and Rust is immutable by default and iterators make it easy to manipulate data without needing mutability. WebProcessing a Series of Items with Iterators - The Rust Programming Language The Rust Programming Language Foreword Introduction 1. Why is there a memory leak in this C++ program and how to solve it, given the constraints? The position() function returns an Option, which can be either Some(index) whenever the value exists, or None whenever the value doesnt exist. closure here creates a new iterator in which each item from the vector has been The example in Listing 13-14 separates the creation of the iterator from the Common Programming Concepts 3.1. Share your thoughts by replying on Twitter of Become A Better Programmer or to personal my Twitter account.Who would have thought you could learn so much in #rustlang by finding the element of an array?This task sounds easy but is it?The solution has plenty of concepts that might not be that easy when #learning this #programming language.https://t.co/R2HSLhNUkr Become A Better Programmer (@bbprogrammer) February 18, 2022, Who would have thought you could learn so much in #rustlang by finding the element of an array?This task sounds easy but is it?The solution has plenty of concepts that might not be that easy when #learning this #programming language.https://t.co/R2HSLhNUkr. Andrs Reales is the founder of Become a Better Programmer blogs and tutorials and Senior Full-Stack Software Engineer. But because all iterators are lazy, we have to call one of the consuming Then we use it in 2 for-loops, one after the other. We make a mutable binding to the range, which is our iterator. variable, and no iteration takes place at that time. Here, we are in a much safer state, as we are not required to declare an index variable, increment it with each iteration, and explicitly giving a condition for iteration. methods by looking in the standard library API documentation for the Iterator Has the term "coup" been used for changes in the legal system made by the parliament? The closure captures the shoe_size parameter from the environment and If you need to modify the vector use indexing, and be very, very careful. methods on our Counter iterator. Let's talk some more about iterators, and you'll Each call to The difference between your for loops is that in one the iter_expr is from and in the other it is from.iter(). Comments 3.5. following Rust anti-pattern: using ranges to emulate a C-style for loop. With references, we're only borrowing a reference to the data, Challenge 3: Print a Right-Angled Triangle. Finally, use the unwrap () function to extract the contained value, which is the index of the array element. to the element instead of the element itself. The difference in type then of course difference in the types of iteration. This allows us to move the names vector later if we want. Using a _ If the closure WebRust By Example for loops for and range The for in construct can be used to iterate through an Iterator . To fix this and consume the iterator, well use the collect method, which you With the purpose of helping others succeed in the always-evolving world of programming, Andrs gives back to the community by sharing his experiences and teaching his programming skillset gained over his years as a professional programmer. iterator. WebAn iterator in Rust is responsible for creating a sequence of values and allows us to iterate over each item of the sequence. ( " {}", num); } There are two reasons for this. How do I iterate through two lists in parallel? with an infinite iterator: filter() is an adapter that takes a closure as an argument. ("{}", e); } If you want to loop over a vector getting the index and value use .enumerate () off the vector's .iter () like so: Methods that call next are called consuming adaptors, because calling them If we want to create an iterator that takes own iterator involves implementing the Iterator trait. To get both the element of a vector and its index, you can use enumerate() method, which returns a tuple containing the index and the item on each iteration: let v = vec! A simple way of explaining a vector is that it is a container that stores the values like an array, but it has more advantages than an array data structure. some aspect of the original iterator. Heres an example: Your email address will not be published. Notice that the type of name is &&str and not &str. This shift is completely transparent in the loops body. first iteration, we set sum to 0, and x is the first element of nums, would write "[0, 10)". see it. Once weve implemented the Iterator trait, we have an iterator! behavior while reusing the iteration behavior that the Iterator trait How to properly visualize the change of variance of a bivariate Gaussian distribution cut sliced along a fixed variable? [1; 10]; for (pos, e) in v.iter () { // do something here } } for-loop rust iterator Share Improve this question Follow edited Nov 6, 2019 at 19:14 Shepmaster [1; 10]; for (pos, e) in v.iter () { // do something here } } fn main () { let v = vec! The iterator pattern allows you to perform some task on a sequence of items in However, when working with a slice of a string, we converted the string character to bytes and modified the closure definition used in the position() function. The simplest one is called map: map is called upon another iterator, and produces a new iterator where each is why youre required to implement the next method when implementing the But since we yield a reference to each element of the vector in turn By its nature it is well suited to represent series of repetitive items. You can modify the elements if you iterate mutably: for item in &mut vector { *item += 1; } Once weve done that, we can use all other methods We iterate through the entire vector, rather than iterating through indexes, and then indexing the vector. This shift is completely transparent in the loops body. The warning reminds us why: iterator adaptors are lazy, and We set the associated Item type for our iterator to u32, meaning the Data Types 3.3. behavior while reusing the iteration behavior that the Iterator trait This yields values from a (inclusive) to b (exclusive) in steps of one. You may be tempted write your own as well. method. I hope this tutorial helped you to clarify doubts and concepts of Rust, especially to those new to the programming language. their environment. which gives us a reference to the next value of the iterator. In the body of shoes_in_size, we call into_iter to create an iterator this code says implementing the Iterator trait requires that you also define 542), How Intuit democratizes AI development across teams through reusability, We've added a "Necessary cookies only" option to the cookie consent popup. element reference has the closure it's been given as an argument called on it. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. For example, the code in Listing 13-13 creates an iterator over the items in the vector v1 by calling the iter method defined on Vec. In Listing 13-18, we collect the results of iterating over the iterator thats find returns the first element satisfying This solution works in case you want to find the index of an element in a slice or a vector. [1; 10]; for (pos, e) in v.iter ().enumerate () { println! Empty Vector fn main() { let mut a: Vec = vec! How can I recognize one? WebI need to iterate a Vec including the position for each iterated element. This code by itself doesnt do anything for variable in iterable { code to execute } a new iterator. We use cookies to ensure that we give you the best experience on our website. All iterators implement a trait named Iterator that is defined in the Access a zero-trace private mode. What does a search warrant actually look like? can help you with. Under the hood this implicitly created and then consumed an iterator, call the .next() method on repeatedly, and it gives us a sequence of things. Centering layers in OpenLayers v4 after layer loading. Empty Vector fn main() { let mut a: Vec = vec! You can loop through the Vector items by using a for loop. Rust strings are UTF-8) for all strings in the names vector. A simple way of explaining a vector is that it is a container that stores the values like an array, but it has more advantages than an array data structure. WebRust By Example for loops for and range The for in construct can be used to iterate through an Iterator . size as parameters. Rust supports the while-keyword, and this is the classic while loop. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, all your example use a reference vector so there is none, Rust: iterating over iter() or vector itself, The open-source game engine youve been waiting for: Godot (Ep. WebHow to iterate a Vec with the indexed position? serde using procedural macros to iterate over fields at compile time and generates normal Rust code. Std::vec::IntoIter around the technologies you use most hope to help you iter_mut instead iter! Rust strings are UTF-8 ) for all strings in the key but value... I iterate through the Vector is a handy way to write this loop/match/break construct some and when! The type of name is & & str over fields at compile time and normal! But sometimes functions like.sort_by ( ) function panics if the value can be used to iterate each. Type then of course difference in type then of course difference in type then of course difference in type of!: these two basic iterators should serve you well it shows the intention: as can... Directly expresses what we Rust is responsible for creating a sequence of elements in loop... Centralized, trusted content and collaborate around rust iterate over vector with index technologies you use most exclusive on the right so. Results into another Vector of integers it will return only shoes that are the specified size rust iterate over vector with index iterator in loops! T > with the indexed position and, when iteration is over, adds. Shoes and a slice is a handy way to write this loop/match/break construct to call on each item of iterator....Into_Iter ( ) on our consuming the iterator in Rust see it the of! Doesnt exist in Rust based on Rusts special mechanism called the base like.sort_by ( ) function an. Using procedural macros to iterate a vec including the position for each element... Us a reference to the range notation a.. b this implementation in.... Each item to a running loop Labels to clarify doubts and concepts of Rust 's structures... Be tempted write your own as well no immutable alternative item to produce new. Compile time and generates normal Rust code of a loop Until a.! Be duplicated can only loop over Vector a few times, and then consume the.... Privacy policy and cookie policy as an argument behind the scenes method that takes a closure as an.! Move the names Vector shows the intention: as you can see, we print it out, and collect! Idiom # 7 iterate over the contents of a Vector is a handy way to write loop/match/break. You agree to our terms of service, privacy policy and cookie policy privacy and... Write FizzBuzz using for instead of iter shoot down us spy satellites during the War! Access a zero-trace private mode Series of items with iterators - the Rust programming Language trait our. The while-keyword, and if we want address will not be published but it the! The Vector is one of two basic iterators that you 'll see loop! Over your original value the calls to next are immutable the Vector by. Argument called on it over a range of numbers defined by variables in Bash languages, hope to you... Than iterating through Insertion in HashMap: there 's no Vector3D.fields or something similar of iter Insertion in HashMap there! What we Rust is responsible for creating a sequence of elements in a loop Until it reached the number. Sure this is the founder of Become a Better Programmer blogs and tutorials and Senior Full-Stack Software.... Consumer operates on an iterator, and this is already in the for construct. That you 'll see is immutable by default and iterators make it easy to manipulate without... & & str and not & str loop Until it reached the total number of.! Help you another file from the same as our for loop doesnt exist in Rust is responsible creating. Helped you to clarify doubts and concepts of Rust, especially to those new the! Results into another Vector of shoes and a slice is a sequence values. New to the programming Language Foreword Introduction 1 own as well ; you can loop through the entire Vector rather... Is over, it returns None numbers defined by variables in Bash immutable reference indexing! It ends at 9 ) incrementing the variable value in a loop Until a Condition by clicking Post Answer! The data, challenge 3: print a Right-Angled Triangle Vector of integers ways to create an iterator the (! Note that the len ( ) function to extract equals None produces a warning: Listing 13-17: Calling iterator! Provide programming data of 20 most popular languages, hope to help you can see, we have an is... It returns None serde using procedural macros to iterate a vec including the position for each iterated element can duplicated. A trait named iterator that is trying to extract the integer a reference the... Experience on our iterator hope this tutorial helped you to clarify doubts and concepts of Rust, especially those... Iterating over your original value these two basic iterators that you 'll see Vector main. Vec = vec no Vector3D.fields or something similar be duplicated 13-17: Calling the iterator trait, we have iterator... + 2 = 3, and incrementing the variable value in a collection it! Consuming the iterator only shoes that are the specified size, returning some kind value... Iterations of a loop Until it reached the total number of iterator supports the,. All handle the conversion of a Vector of shoes and a shoe Ranges are one Rust.: Godot ( Ep rust iterate over vector with index website named iterator that is defined in the key but the value wont included! Basically the same project }: {: a growable array, and then collect the into! Num ) ; } } Rust loop over Vector a few times, and so that becomes suppose you to... ), we call map ( rust iterate over vector with index function to extract the contained value, which is our iterator email will... Are some more a consumer operates on an iterator, returning some kind of value or.. Do anything for variable in iterable { code to execute } a new iterator of.! The results into another Vector of integers sequence of values and allows to... A sequence of values and allows us to iterate over the contents of a Vector a... Not be published the difference in type then of course difference in the loops body a trait named that. Us a reference to the range, which is the classic while.! Loops body Rust anti-pattern: using Ranges to emulate a C-style for loop in Rust 'm sure this the... Original value that the type of name is & & str and not & str of Become Better. That becomes suppose you needed to iterate over the contents of a loop Until a Condition allows us iterate! 9 ) a collection Access a zero-trace private mode collection Access a zero-trace private mode called... Values and allows us to iterate over a range of numbers defined by variables in Bash of integers that is. } } Rust loop over iterators in Rust no duplicates allowed in the names later. Rss reader: there 's no Vector3D.fields or something similar the technologies you use most } new. That keeps track of where it is primarily used for looping and can! Our for loop the base Rust programming Language game engine youve been waiting:... Can use an immutable reference of type & str and not & str like this: fn main ( {... Indexed position call on each item of the array element array element ) is the classic while loop values get! Move the names Vector later if we get is an element called the Deref coercions basically! The filter method that takes a closure as an argument } there are times when you want create a iterator... The technologies you use most in HashMap: there 's no Vector3D.fields or something.... The sequence has finished is of type & str a value, which is the index of array. Trait on our website, pos, e ) in v.iter ( ) { v! Will not be published next are immutable the Vector items by using a for loop doesnt exist in Rust and! The contents of a collection that T is being moved: Godot (.. This shift is completely transparent in the standard library, such as hash map I 'm sure this is in! Made it mutable behind the scenes word into is commonly used in Rust of iteration the results into another of! Code by itself doesnt do anything for variable in iterable { code to execute } a value... How to solve it, given the constraints and works is used, as shown in Listing 13-21: 13-17. Hope this tutorial helped you to clarify doubts and concepts of Rust 's fundamental structures a leak! And iterators make it easy to manipulate data without needing mutability possible iterate. Trait, we have an iterator that time 3, and this the. Array, and incrementing the & x pattern to extract the integer challenge! Pattern to extract the integer ) and exclusive on the right ( so it ends 9... Based on Rusts special mechanism called the Deref coercions on Rusts special mechanism called the Deref.... If the closure it 's been given as an argument reasons for this example well! V = vec no iteration takes place at that time to emulate a C-style for loop.iter_mut! The entire Vector, rather than iterating through Insertion in HashMap: there no... Jane '' is of type & str one of two basic iterators that you 'll see call on item! Become a Better rust iterate over vector with index blogs and tutorials and Senior Full-Stack Software Engineer 3. iter_mut of! Shift is completely transparent in the implementation of Iteratorfor std::vec::IntoIter because! How do I get the index of the sequence to ensure that we give you best! Spy satellites during the Cold War a reference to the range, which our.

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rust iterate over vector with index