Category: C++

Another day, another compiler/library bug. If you’re unfortunate enough to still be using Visual Studio 2010, don’t use tuples as map keys. #include #include #include using namespace std; typedef tuple FooT; typedef map MapT; int main(int, char*[]) { MapT m; // put a value in the map { FooT f(nullptr,…

C++ lambdas are wonderful for all sorts of reasons (especially with their C++14-and-beyond power). But I’ve run into a problem that I can’t think of a good way around yet. If you’re up to date with C++, of course you know that rvalue references and move semantics are a major…

Consider the following code: #include #include using namespace std; // base template template struct what_type { void operator()() { cout

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript Refactoring! My initial plan for customizing opener/closer/separator for containers turned out to be unwieldy: I realized that it wouldn’t be possible for me to provide default specializations and also allow clients to specialize. Also, you may have noticed that…

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript So far, we can print containers, but what about arrays? And what about “pretty-printing” strings – perhaps we need to wrap them with quotes. Well, we know that with the existing code, both arrays and strings count as outputtable….

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript Callable things. There are several types: functions member functions std::functions bind expressions lambdas objects that support operator() (function objects) So, going back to my tag code, so far (with everything I’ve added) and including callable things, it will look…

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript So far, we’ve dealt with things that are already outputtable with operator<<, and things that are iterable with begin() and end(). To round out the “containers”, we need to deal with pair and tuple. It’s simple to print a…

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript We have a basic plan, and the ability to detect concrete types. But how can we detect whether an object supports output with operator<<? For this, there is a recently-discovered amazing trick. Here’s the code: template using void_t =…

Part 1 Part 2 Part 3 Part 4 Part 5 Postscript I thought I’d have a go at writing some code that could print things. A pretty-printer, if you like. What I want to be able to do is this: // Print x correctly, where x is ANY type. cout

(following on from C++ Guru Question) There are a few reasons why the code before didn’t work: mainly a) C++ template argument deduction works one-way with a list of candidates, it’s not H-M type inference. b) A C++ lambda is a thing with some internal type, not a std::function (although…