Better way to say x == Foo::A || x == Foo::B || x == Foo::C || …?

Question

Let\'s say I have a bunch of well-known values, like this (but const char * is just an example, it could be more complicated):

const char *A = \"A\"         


        

Answer 1

(Edit: Turns out my original trick with a dummy type didn't work, I was misled by a lucky accident in my tests. Let's try that again...)

With a couple of helper templates you can write a general solution for this kind of situation:

template  class Matcher {
public:
    explicit Matcher(T1 t1): val(t1), flag(false) {}
    template  Matcher& operator()(T2 t2)
        { flag |= val == t2; return *this; }
    operator bool() const { return flag; }
private:
    T1 val;
    bool flag;
};
template  Matcher match(T1 t1) { return Matcher(t1); }

// example...
string s = whatever;
if (match(s)("foo")("bar")("zap")) { do_something(); }

You can match against as many arguments as you want.