iterator

问题 I have a vector storing {1,2,3,4,5}. I tried to print *(vec.end()) and got back the result 6. I don't know how to explain this. Similarly, calling vec.find(500) gave the result 6. Why am I getting this number? #include<iostream> #include<iterator> #include<set> #include<map> int main() { int a[] = {1,2,3,4,5}; std::set<int> set1(a,a+sizeof(a)/sizeof(int)); for (std::set<int>::iterator itr=set1.begin();itr!=set1.end();++itr){ std::cout << *itr << std::endl; } //std::pair<std::set<int>:

问题 Is an iterable the same as an iterator, or are they different? It seems, from the specifications, an iterable is an object, say, obj , such that obj[Symbol.iterator] refers to a function, so that when invoked, returns an object that has a next method that can return a {value: ___, done: ___} object: function foo() { let i = 0; const wah = { next: function() { if (i <= 2) return { value: (1 + 2 * i++), done: false } else return { value: undefined, done: true } } }; return wah; // wah is

问题 Is an iterable the same as an iterator, or are they different? It seems, from the specifications, an iterable is an object, say, obj , such that obj[Symbol.iterator] refers to a function, so that when invoked, returns an object that has a next method that can return a {value: ___, done: ___} object: function foo() { let i = 0; const wah = { next: function() { if (i <= 2) return { value: (1 + 2 * i++), done: false } else return { value: undefined, done: true } } }; return wah; // wah is

问题 I am trying to create an mutable iterator for a vector of type: Vec<Vec<(K, V)>> The iterator code: pub struct IterMut<'a, K: 'a, V: 'a> { iter: &'a mut Vec<Vec<(K, V)>>, ix: usize, inner_ix: usize, } impl<'a, K, V> Iterator for IterMut<'a, K, V> { type Item = (&'a K, &'a mut V); #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { while self.iter.len() < self.ix { while self.iter[self.ix].len() < self.inner_ix { self.inner_ix += 1; let (ref k, ref mut v) = self.iter[self.ix][self

问题 I am trying to create an mutable iterator for a vector of type: Vec<Vec<(K, V)>> The iterator code: pub struct IterMut<'a, K: 'a, V: 'a> { iter: &'a mut Vec<Vec<(K, V)>>, ix: usize, inner_ix: usize, } impl<'a, K, V> Iterator for IterMut<'a, K, V> { type Item = (&'a K, &'a mut V); #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { while self.iter.len() < self.ix { while self.iter[self.ix].len() < self.inner_ix { self.inner_ix += 1; let (ref k, ref mut v) = self.iter[self.ix][self

问题 I am trying to understand when an iterator::value_type is actually used. Because, all operators of iterators, seem to use only iterator::pointer and iterator::reference . Question: Is iterator::value_type actually used for something? Extra question: Would an iterator inherited from std::iterator<std::random_access_iterator_tag, int, std::ptrdiff_t, bool*, bool&> raise some semantic issues? EDIT: To understand why I am asking this question, it's because I am working on an iterator for a type

问题 I am writing a command line application in rust for processing audio from a sensor. I would like the user to be able to choose an algorithm or filter to apply from several options. I was hoping to use dynamic dispatch to switch out a struct which implements my filter trait at runtime. However, this is not allowed by the compiler, because one of the trait methods takes a generic parameter. How could I implement this same functionality, without causing any compiler troubles? I know that an easy

问题 I am writing a command line application in rust for processing audio from a sensor. I would like the user to be able to choose an algorithm or filter to apply from several options. I was hoping to use dynamic dispatch to switch out a struct which implements my filter trait at runtime. However, this is not allowed by the compiler, because one of the trait methods takes a generic parameter. How could I implement this same functionality, without causing any compiler troubles? I know that an easy

问题 Is it specified that you can delete any element in an instance of Set while iterating using for..of and that you won't iterate more than once on an element you won't miss any other element that was in the set at the start of the iteration other than the ones you remove ? 回答1: Yes , it is perfectly fine to add elements and remove elements to a set while iterating it. This use case was considered and is supported in JavaScript 2015 (ES6). It will leave it in a consistent state. Note this also

问题 Is it specified that you can delete any element in an instance of Set while iterating using for..of and that you won't iterate more than once on an element you won't miss any other element that was in the set at the start of the iteration other than the ones you remove ? 回答1: Yes , it is perfectly fine to add elements and remove elements to a set while iterating it. This use case was considered and is supported in JavaScript 2015 (ES6). It will leave it in a consistent state. Note this also