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…
How to print anything in C++ (part 5)
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….
How to print anything in C++ (part 4)
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…
How to print anything in C++ (part 3)
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…
How to print anything in C++ (part 2)
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 =…
How to print anything in C++ (part 1)
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
Holy Wars
All right, I have some opinions. Here are the definitive answers to the three most important dilemmas facing programmers today 🙂 * Static typing vs Dynamic typing Static typing. I suppose dynamic types are OK if you’re hacking together a small tool. But static (strong, preferably HM-inferred) typing allows you…
Do-notation can be misleading
Consider the following function: oddness :: Maybe Int oddness = do let a = Just 1 :: Maybe Int b >= \b -> return b And recall the definition of (>>=) for Maybe: instance Monad Maybe where (Just x) >>= k = k x Nothing >>= _ = Nothing So…
C++ Guru Question – followup
(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…
C++ Guru Question
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 =…