I learn iterators and exactly speaking copied code below, and got error: expected integer, found &{integer} let v = [1, 2, 3]; let mut iter = v.into_iter(); assert_eq!(Some(1), iter.next()); assert_eq!(Some(2), iter.next()); assert_eq!(Some(3), iter.next()); assert_eq!(None, iter.next()); Appreciate explanation what I do wrong, while copied code from documentation does not work. The error I got the every… Read More expected integer, found `&{integer}`

Code: pub fn iter(&self) -> impl Iterator<Item = (&usize, &T)> + ‘_ { self.values.iter().map(|(key, value)| (key, value)) } Quoted from here, it seems following is enough: pub fn iter(&self) -> impl Iterator<Item = (&usize, &T)> + ‘_ { self.values.iter() } Any difference? >Solution : Yes, the former returns a type that implements Iterator<Item = (&usize,… Read More Does the `map` call serve any purpose here?

I’m trying to code a set of functions for a game’s inventory, but the function to remove an item from the inventory has become a road block. Essentially all it needs to do is find the record of a particular item in the vector, and remove it. Running the code below produces about 60 lines… Read More find() causing "template argument" compilation errors when using struct as input. Any suggestions?

I have the following code converting from Vec<Result<Option<T>, E>> to Result<Vec<T>, E> but I’m wondering if there’s something I don’t know about iterators that could simplify it even more/make the code more concise. fn clean<T, E>(data: Vec<Result<Option<T>, E>>) -> Result<Vec<T>, E> { data.into_iter() .filter_map(|i| match i { Ok(Some(a)) => Some(Ok(a)), Ok(None) => None, Err(e) =>… Read More Shorter way to convert Vec<Result<Option<T>, E>> to Result<Vec<T>, E>

vector.data() should return a pointer to the first element, but when I use it on a vector<uint8_t>, it somhow returns somthing else: int main() { std::string myString = {"a b c all the way long"}; std::vector<uint8_t> myVec(myString.begin(), myString.end()); std::cout << myVec.data() << std::endl; std::vector<int> anotherVec = {4,5,2,3}; std::cout<< anotherVec.data() << std::endl; return 0; } program… Read More How to correctly use vector<uint8_t>.data()?

I’ve seen a few iterators implemented in javascript, and every time it seems like they’re off by one (there’s obviously something I’m missing) Here’s an example const numbers = [1, 2, 3]; numbers[Symbol.iterator] = function() { let idx = 0; return { next: function() { return { value: numbers[idx++], done: idx > numbers.length, }; },… Read More When to set "done" to true in an iterator in javascript (off by one errors)

Apologies if this is long winded, I want to make myself as clear as I can be. Ok so here is what I would like this code to do: Create a peekable iterator out of some values loop and Consume the elements of the iterator and check what they are Depending on what each element… Read More How can one pass an iterator to a method that consumes some of it?

#include <iostream> #include <functional> #include <list> #include <iterator> int reduce (std::list<int> l,std::function<int(int a,int b)> f,int start){ int sum=start; for(auto i1=l.begin();i1!=l.end();++i1){ auto i2=++i1; sum+=f((*i1),(*i2)); ++i2; } return sum; } int main(){ std::list<int> list{11,4,5,12,6,8,9}; auto a=[](int a,int b){return a+b+1;}; int start=-12; int o=reduce(list,a,start); std::cout<<"Output: "<< o<<std::endl; } I have to write a reduce function that takes a… Read More iterating through list and using each two elements as function arguments

#include <iostream> #include <list> using namespace std; int main() { list<int> A; A.push_back(1); A.push_back(2); A.push_back(3); auto it = A.begin(); cout << *it << ‘ ‘; advance(it, 1); cout << *it << ‘ ‘; advance(it, 1); cout << *it << ‘ ‘; advance(it, 1); cout << *it << ‘ ‘; advance(it, 1); cout << *it <<… Read More The behavior of std::advance at the end of std::list