Category: C++

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 like: template using stringifier_tag =… Continue reading How to print anything in C++ (part 4)

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 pair: template struct stringifier_select {… Continue reading How to print anything in C++ (part 3)

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 = void; template using operator_output_t =… Continue reading How to print anything in C++ (part 2)

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 it can be assigned to… Continue reading C++ Guru Question – followup

Wondering about this… template argument deduction succeeds for the explicitly-typed variable, fails in the auto case. (Also, it succeeds either way for an equivalently-typed unary operator template). template struct Foo { T m_t; }; template Foo operator/=(Foo foo, function fn) { return fn(foo.m_t); } void mystery() { auto foo = Foo{1}; // this works… function… Continue reading C++ Guru Question

I recently discovered a C++ technique I haven’t seen recognized before in any books, articles, or mentioned online anywhere (search terms are difficult perhaps). For want of a better name I call it Structural Capture. Consider the following code: #include #include using namespace std; //————————————————————— struct Foo { template Foo(const T& t) { m_outputFunc =… Continue reading An Interesting C++ Technique