It’s compiling because printf isn’t type safe, since it uses variable arguments in the C sense1. printf has no option for std::string, only a C-style string. Using something else in place of what it expects definitely won’t give you the results you want. It’s actually undefined behaviour, so anything at all could happen. The easiest … Read more
There’s a function std::reverse in the algorithm header for this purpose. #include <vector> #include <algorithm> int main() { std::vector<int> a; std::reverse(a.begin(), a.end()); return 0; }
As I mention here, I’ve seen Intel TBB’s custom STL allocator significantly improve performance of a multithreaded app simply by changing a single std::vector<T> to std::vector<T,tbb::scalable_allocator<T> > (this is a quick and convenient way of switching the allocator to use TBB’s nifty thread-private heaps; see page 7 in this document)
There’s a function to find a substring within a string (find), and a function to replace a particular range in a string with another string (replace), so you can combine those to get the effect you want: bool replace(std::string& str, const std::string& from, const std::string& to) { size_t start_pos = str.find(from); if(start_pos == std::string::npos) return … Read more
add #include <iostream> to the start of io.cpp too.
You have to increment the iterator first (with i++) and then remove the previous element (e.g., by using the returned value from i++). You can change the code to a while loop like so: std::list<item*>::iterator i = items.begin(); while (i != items.end()) { bool isActive = (*i)->update(); if (!isActive) { items.erase(i++); // alternatively, i = … Read more
I have thought about this question quite a bit over the past four years. I have come to the conclusion that most explanations about push_back vs. emplace_back miss the full picture. Last year, I gave a presentation at C++Now on Type Deduction in C++14. I start talking about push_back vs. emplace_back at 13:49, but there … Read more
The “STL” was written by Alexander Stepanov in the days long before C++ was standardised. C++ existed through the 80s, but what we now call “C++” is the language standardised in ISO/IEC 14882:2014 (and earlier versions, such as ISO/IEC 14882:2011). The STL was already widely used as a library for C++, giving programmers access to … Read more
You can use std::find from <algorithm>: #include <algorithm> #include <vector> vector<int> vec; //can have other data types instead of int but must same datatype as item std::find(vec.begin(), vec.end(), item) != vec.end() This returns an iterator to the first element found. If not present, it returns an iterator to one-past-the-end. With your example: #include <algorithm> #include … Read more
Consider two libraries called Foo and Bar: using namespace foo; using namespace bar; Everything works fine, and you can call Blah() from Foo and Quux() from Bar without problems. But one day you upgrade to a new version of Foo 2.0, which now offers a function called Quux(). Now you’ve got a conflict: Both Foo … Read more