iterator

问题 I'm trying to complete the activity at the bottom of this page, where I need to print the index of each element as well as the value. I'm starting from the code use std::fmt; // Import the `fmt` module. // Define a structure named `List` containing a `Vec`. struct List(Vec<i32>); impl fmt::Display for List { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { // Extract the value using tuple indexing // and create a reference to `vec`. let vec = &self.0; write!(f, "[")?; // Iterate over

问题 I'm trying to complete the activity at the bottom of this page, where I need to print the index of each element as well as the value. I'm starting from the code use std::fmt; // Import the `fmt` module. // Define a structure named `List` containing a `Vec`. struct List(Vec<i32>); impl fmt::Display for List { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { // Extract the value using tuple indexing // and create a reference to `vec`. let vec = &self.0; write!(f, "[")?; // Iterate over

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 4 years ago . Improve this question /* I have a list of employees */ List<Employee> empList=new ArrayList<Employee>(); empList.add(employee1); empList.add(employee2); empList.add(employee3); empList.add(employee4); /* I have taken an iterator */ Iterator<Employee> empIterator=empList.iterator()

问题 When I'm using a std::unordered_map<K, V> I know that the iterator to each key-value pair is of type std::unordered_map<K, V>::iterator . I also know that the iterator itself points to a pair<const K, V> . However, the only reason I know the iterator points to a pair is from looking at example code. Where is this behavior defined? For example, if I go to the documentation at cppreference.com, I don't see where this behavior is explained. It only says that the member iterator is defined as a

问题 I wonder what happens if I have an iterator on the last element of the vector and do pop_back . std::set<int> s; s.insert(5); std::vector<int> v = {1, 2, 3, 4, 5}; for (auto it = v.begin(); it != v.end();) { if (s.count(*it)) { std::swap(*it, v.back()); v.pop_back(); } else { ++it; } } Code above works properly ( v is {1, 2, 3, 4} after that block) at least with clang, but is it correct to check if it == v.end() if it is invalidated? 回答1: Your instincts are good; vector::pop_back invalidates

问题 In my code I often have functions doing the same thing on different iterable Qt Container types, for instance: void removeX(QMap<qint64, QString> & map) { QMutableMapIterator<qint64, QString> it(map); while (it.hasNext()) { it.next(); if (it.value() == "X") it.remove(); } } void removeX(QList<QString> & list) { QMutableListIterator<QString> it(list); while (it.hasNext()) { it.next(); if (it.value() == "X") it.remove(); } } (and I know there is already a removeAll function in QList. This is

问题 I'm trying to do something like this: import asyncio from itertools import islice async def generate_numbers(n): for x in range(n): yield x async def consume_numbers(n): async for x in generate_numbers(n): print(x) async def consume_some_numbers(n,m): async for x in islice(generate_numbers(n),m): #<-- This doesn't work. islice doesn't recognize async iterators as iterators. print(x) loop = asyncio.get_event_loop() loop.run_until_complete(consume_numbers(10)) loop.run_until_complete(consume

问题 I have a question, which very likely has been asked like this before, because I think what I want is something that a considerable amount of people would want. However I could not come up with any way of expressing it that would return what I wanted in search (not google, not here). So maybe the answer here is just a single term used to describe what I mean. What I want to implement is something that roughly does the following: It can take a functor struct/class and generate a sequence of

问题 Let's say I have a list that contains 10,000+ proxies proxy_list = ['ip:port','ip:port',.....10,000+ items] How do I iterate it to get the proxies that works for my pc? Using the following code it is possible to find it , but takes 5*10,000 seconds to get completed. How would I iterate through the list faster? import requests result=[] for I in proxy_list: try: requests.get('http:\\www.httpbin.org\ip',proxies = {'https' : I, 'http' : I } ,timeout = 5) result.append(I) except: pass 回答1: You

问题 Let's say I have a list that contains 10,000+ proxies proxy_list = ['ip:port','ip:port',.....10,000+ items] How do I iterate it to get the proxies that works for my pc? Using the following code it is possible to find it , but takes 5*10,000 seconds to get completed. How would I iterate through the list faster? import requests result=[] for I in proxy_list: try: requests.get('http:\\www.httpbin.org\ip',proxies = {'https' : I, 'http' : I } ,timeout = 5) result.append(I) except: pass 回答1: You