iterator

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 6 years ago . Improve this question I need to remove an item from a generic list in java, but I don't know how to do this. If it was a list of int, I would just set it to zero, if it was strings I would set it to null. How can I do this with a generic list, and I can't use an methods of Arraylist or anything

问题 What is the difference between iterators and generators? Some examples for when you would use each case would be helpful. 回答1: iterator is a more general concept: any object whose class has a __next__ method ( next in Python 2) and an __iter__ method that does return self . Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions ( yield statements, in Python 2.5 and earlier), and is an object that meets the previous

问题 What is the difference between iterators and generators? Some examples for when you would use each case would be helpful. 回答1: iterator is a more general concept: any object whose class has a __next__ method ( next in Python 2) and an __iter__ method that does return self . Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions ( yield statements, in Python 2.5 and earlier), and is an object that meets the previous

问题 What is the difference between iterators and generators? Some examples for when you would use each case would be helpful. 回答1: iterator is a more general concept: any object whose class has a __next__ method ( next in Python 2) and an __iter__ method that does return self . Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions ( yield statements, in Python 2.5 and earlier), and is an object that meets the previous

问题 According to the documentation, a container that needs to be iterable should supply an __iter__() function to return an iterator. The iterator itself is required to follow the iterator protocol, meaning that it has to provide __iter__() that returns itself, and __next__() that provides the next item, or raises a StopIterator exception. Now I understand why both of those would be required in a container that does its own iteration, since you have to both provide an iterator and a next item:

问题 According to the documentation, a container that needs to be iterable should supply an __iter__() function to return an iterator. The iterator itself is required to follow the iterator protocol, meaning that it has to provide __iter__() that returns itself, and __next__() that provides the next item, or raises a StopIterator exception. Now I understand why both of those would be required in a container that does its own iteration, since you have to both provide an iterator and a next item:

问题 std::set<int> s = { 1,2,3,4,5 }; std::set<int> s2(s.begin(), s.begin() + 2); I want to assgin several values of s into s2 . But got below compile error: Error C2676 binary ' + ': ' std::_Tree_const_iterator<std::_Tree_val<std::_Tree_simple_types<_Ty>>> ' does not define this operator or a conversion to a type acceptable to the predefined It seems std::set::const_iterator doesn't have operator+ method. 回答1: It seems std::set::const_iterator doesn't have operator+ method. You are right about

问题 std::set<int> s = { 1,2,3,4,5 }; std::set<int> s2(s.begin(), s.begin() + 2); I want to assgin several values of s into s2 . But got below compile error: Error C2676 binary ' + ': ' std::_Tree_const_iterator<std::_Tree_val<std::_Tree_simple_types<_Ty>>> ' does not define this operator or a conversion to a type acceptable to the predefined It seems std::set::const_iterator doesn't have operator+ method. 回答1: It seems std::set::const_iterator doesn't have operator+ method. You are right about

问题 It seems natural to have an std::iterator for std::tuple . However it is not implemented, so programmers implement there own versions. One is for example found at Jonathan Müller's Blog. Do I overlook something? Is there any reason why there is no "official version" for an tuple_iterator? 回答1: std::tuple is not a container, at least not in the sense of the standard library containers. It cannot be iterated with the usual methods because it holds objects of different types. Standard containers

问题 Consider the following code: let u: Vec<u8> = (64..74).collect(); let v: Vec<u8> = u.iter().map(|i| i + 1).collect(); u was not moved, therefore v was inevitably newly allocated. But if I do the following: let w: Vec<u8> = u.into_iter().map(|i| i + 1).collect(); u was moved and w is the name of its transformation. Here is some pseudo-code representing what I mean: mark u as "moved" for i = 0..10: u[i] += 1 w = u There is (in my opinion) no need for a new allocation, since we map a type to