int main(int argc, char* argv[]) ?

if(argv[1] == +)
{
cout<<a + b;
}
else
{
cout<<a - b;
}

#include <iostream>
#include <cstring>
 
int main(int argc, char *argv[])
{
    if (argc < 2)
        return 1;
    
    bool plus_enabled = false;
    bool minus_enabled = false;
    
    for (int i = 1; i < argc; ++i)
    {
        if (strcmp(argv[i], "+") ==  0)
            plus_enabled = true;
        else if (strcmp(argv[i], "-") == 0)
            minus_enabled = true;
    }
    
    if (plus_enabled)
        std::cout << "plus enabled\n";
    if (minus_enabled)
        std::cout << "minus enabled\n";
}

#include <iostream>
 
template<class Val> struct swither
{
    swither(const Val& v)
        : val(v)
    {}
 
    void operator()()const noexcept {}
 
    template <class E, class F, class ... Args>
    void operator()(E&& e, F&& f, Args&& ... args) const 
    {
        if(e == val)
            f(); 
        else
            (*this)(std::forward<Args>(args)...);
    }
private:
    Val val;
};
 
template<class Val> auto Swith(const Val& v)
   { return swither<Val>(v); }
 
#define dCASE(n) n,[]()
 
int main()
{
    auto x = "trololo";
    
    Swith(x) (
        
        dCASE("ololo")   { std::cout <<"ololo\n";   },
        dCASE("trololo") { std::cout <<"trololo\n"; } 
    );
}