istream-iterator

问题 I tried implementing an example of stream iterators from page 107 of "The C++ Standard Library". I get stuck on this line: copy (istream_iterator<string>(cin), istream_iterator<string>(), back_inserter(coll)); The program keeps reading data from the console here, but does not pass on to the next line. How do I continue past this point? 回答1: take for instance, if you would have made an input stream of int then you would have given input like - 45 56 45345 555 ....., so in all those cases, the

问题 I was reading Constructing a vector with istream_iterators which is about reading a complete file contents into a vector of chars. While I want a portion of a file to be loaded in to a vector of chars. #include <iostream> #include <fstream> #include <iterator> #include <vector> #include <algorithm> using namespace std; int main(int argc, char *argv[]) { ifstream ifs(argv[1], ios::binary); istreambuf_iterator<char> beginItr(ifs); istreambuf_iterator<char> endItr(beginItr); advance(endItr, 4);

问题 Why does the following code output c ? // main.cpp #include <iostream> #include <sstream> #include <iterator> int main( int argc, char* argv[] ) { std::string p( "abcdefghijklmnopqrstuvwxyz" ); std::stringstream ss(p); std::istream_iterator<char> i( ss ); std::istream_iterator<char> j( ss ); std::istream_iterator<char> k( ss ); std::cout << *k << std::endl; return 0; } . $ g++ --version g++ (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1) Copyright (C) 2019 Free Software Foundation, Inc. This is free

问题 I have tried to write a code to read strings from file named "test.txt" and write the strings to standard output. The code below works well: int main() { using namespace std; ifstream file("test.txt"); copy(istream_iterator<string>(file), istream_iterator<string>(), ostream_iterator<string>(cout, " ")); } However, with this modification, the code no longer compiles: int main() { using namespace std; copy(istream_iterator<string>(ifstream("test.txt")), // <-- Error here istream_iterator<string

问题 I have a legacy code in which the interface is defined for pointer. I am trying to adapt some functions to take iterators, e.g. forward iterators. Is one allowed to take the address of the element dereferenced by InputIterator such as istream_iterator ? The result is a temporary and has to be is somewhere in memory for the life of the call, but I am not sure. The following example uses double , but the type can be more complicated (large). #include<iostream> #include<iterator> #include

问题 So given the definitions: typedef char Task; struct Tache { char step; int duration; list<Task> precedentTask; }; I've written an extraction operator for Tache : istream& operator>>(istream& lhs, Tache& rhs) { string line; getline(lhs, line, '\n'); stringstream ss(line); ss >> rhs.step; ss.ignore(numeric_limits<streamsize>::max(), '('); ss >> rhs.duration; ss.ignore(numeric_limits<streamsize>::max(), ')'); const regex re("\\s*,\\s*([a-zA-Z])"); string precedentTasks; getline(ss,

问题 I have a legacy code in which the interface is defined for pointer only and I am trying to adapt some functions to take iterators. In the answers to this question Address of a dereferenced InputIterator? The case of istream_iterator it was noted that std::istream_iterators are InputIterator . However they are special among InputIterator s, because their dereference is guarantied to generate a language reference T const& . The code for a general input iterator would look like this, notice that

问题 Given a file containing the following hex code: 0B 00 00 00 00 00 20 41 I'm trying to populate an std::vector <std::uint8_t> and then checking each byte manually. Here's the code where I create my vector from two std::istream_iterators using the iterator constructor using Bytes = std::vector<std::uint8_t>; using ByteItr = std::istream_iterator<std::uint8_t>; Bytes getBytes() { std::ifstream in; in.open("filepath"); in.seekg(0, std::ios::beg); Bytes bytes; ByteItr start(in); ByteItr end;

问题 I'm trying to code opposite action to this: std::ostream outs; // properly initialized of course std::set<int> my_set; // ditto outs << my_set.size(); std::copy( my_set.begin(), my_set.end(), std::ostream_iterator<int>( outs ) ); it should be something like this: std::istream ins; std::set<int>::size_type size; ins >> size; std::copy( std::istream_iterator<int>( ins ), std::istream_iterator<int>( ins ) ???, std::inserter( my_set, my_set.end() ) ); But I'm stuck with the 'end' iterator --

问题 I want to be able to solve problems like this: Getting std :: ifstream to handle LF, CR, and CRLF? where an istream needs to be tokenized by a complex delimiter; such that the only way to tokenize the istream is to: Read it in the istream a character at a time Collect the characters When a delimiter is hit return the collection as a token Regexes are very good at tokenizing strings with complex delimiters: string foo{ "A\nB\rC\n\r" }; vector<string> bar; // This puts {"A", "B", "C"} into bar