I’d say the exceptions that vector::at() throws aren’t really intended to be caught by the immediately surrounding code. They are mainly useful for catching bugs in your code. If you need to bounds-check at runtime because e.g. the index comes from user input, you’re indeed best off with an if statement. So in summary, design … Read more
EDIT: using c++14, the best solution is very easy to write thanks to lambdas that can now have parameters of type auto. This is my current favorite solution std::sort(v.begin(), v.end(), [](auto &left, auto &right) { return left.second < right.second; }); ORIGINAL ANSWER: Just use a custom comparator (it’s an optional 3rd argument to std::sort) struct … Read more
You need to use a back_inserter: std::copy(input.begin(), input.end(), std::back_inserter(output)); std::copy doesn’t add elements to the container into which you are inserting: it can’t; it only has an iterator into the container. Because of this, if you pass an output iterator directly to std::copy, you must make sure it points to a range that is at … Read more
In C++11, this is the preferred way: std::vector<X> f(); That is, return by value. With C++11, std::vector has move-semantics, which means the local vector declared in your function will be moved on return and in some cases even the move can be elided by the compiler.
valarray is kind of an orphan that was born in the wrong place at the wrong time. It’s an attempt at optimization, fairly specifically for the machines that were used for heavy-duty math when it was written — specifically, vector processors like the Crays. For a vector processor, what you generally wanted to do was … Read more
Yes, std::vector<T>::push_back() creates a copy of the argument and stores it in the vector. If you want to store pointers to objects in your vector, create a std::vector<whatever*> instead of std::vector<whatever>. However, you need to make sure that the objects referenced by the pointers remain valid while the vector holds a reference to them (smart … Read more
std::fill(v.begin(), v.end(), 0);
If you have a C++11 compiler, I would suggest using a range-based for-loop (see below); or else use an iterator. But you have several options, all of which I will explain in what follows. Range-based for-loop (C++11) In C++11 (and later) you can use the new range-based for-loop, which looks like this: std::vector<char> path; // … Read more
If you have a C++11 compiler, I would suggest using a range-based for-loop (see below); or else use an iterator. But you have several options, all of which I will explain in what follows. Range-based for-loop (C++11) In C++11 (and later) you can use the new range-based for-loop, which looks like this: std::vector<char> path; // … Read more
vector1.insert( vector1.end(), vector2.begin(), vector2.end() );