Enums aren’t lvals, static member values are and if passed by reference the template will be instanciated: void f(const int&); f(TMPFib<1>::value); If you want to do pure compile time calculations etc. this is an undesired side-effect. The main historic difference is that enums also work for compilers where in-class-initialization of member values is not supported, … Read more
I think in Ruby 1.9 you can do this: class A define_singleton_method :loudly do |message| puts message.upcase end end A.loudly “my message” # >> MY MESSAGE
Identical literal strings are not guaranty to be identical, but you can build type from it which can compare identical (without comparing string), something like: // Sequence of char template <char…Cs> struct char_sequence { template <char C> using push_back = char_sequence<Cs…, C>; }; // Remove all chars from char_sequence from ‘\0’ template <typename, char…> struct … Read more
Just in case, here is what I meant by hiding ViewOf inside a type class (type classes is an alternative to match types). Sadly, in Scala 3 this is wordy. (version 1) import scala.annotation.experimental import scala.quoted.{Expr, Quotes, Type, quotes} // Library part trait View extends Selectable { def applyDynamic(key: String)(args: Any*): Any = { println(s”$key … Read more
A trait you want might look like this: template <typename B, typename D> struct is_base_of // check if B is a base of D { typedef char yes[1]; typedef char no[2]; static yes& test(B*); static no& test(…); static D* get(void); static const bool value = sizeof(test(get()) == sizeof(yes); }; Then you just need a static … Read more
Module inspect from Python’s standard library is your friend — see the online docs! inspect.getargspec(func) returns a tuple with four items, args, varargs, varkw, defaults: len(args) is the “primary arity”, but arity can be anything from that to infinity if you have varargs and/or varkw not None, and some arguments may be omitted (and defaulted) … Read more
Claudiu’s answer is correct, but you can also cheat by getting the class name off of the self argument. This will give misleading log statements in cases of inheritance, but will tell you the class of the object whose method is being called. For example: from functools import wraps # use this to preserve function … Read more
You can dynamically add a classmethod to a class by simple assignment to the class object or by setattr on the class object. Here I’m using the python convention that classes start with capital letters to reduce confusion: # define a class object (your class may be more complicated than this…) class A(object): pass # … Read more
[*] TL;DR: This “empty __class__ cell” error will happen when the metaclass tries to call a method in the defined class (or instantiate it) before it is done with its __new__ and __init__,and the called method uses super. The error will also happen if one writes a call to super() in a function defined outside … Read more
send sends a message to an object instance and its ancestors in class hierarchy until some method reacts (because its name matches the first argument). Practically speaking, those lines are equivalent: 1.send ‘+’, 2 1.+(2) 1 + 2 Note that send bypasses visibility checks, so that you can call private methods, too (useful for unit … Read more