with scoped

gistfile1.txt

// [std-proposals] Using the underscore for unused identifiers
// https://groups.google.com/a/isocpp.org/d/msg/std-proposals/a4CRu2KONZ8/N0aPF76B990J

#include <iostream>

// _, or ANON
#define with( expr )  if ( auto&& _ = (expr) )

struct wither
{
    operator bool() { return true; }
};

struct scoped : wither
{
    const char c;
    scoped(char c) :c(c)  { std::cout <<  "scoped(" << c << ")\n"; };
    ~scoped()             { std::cout << "~scoped(" << c << ")\n"; };

    scoped( scoped && other ) : c(other.c) { }
};

int main()
{
    with ( scoped('a') )
    {
        std::cout << "{ block-1 }\n";

        with ( scoped('b') )
        {
            std::cout << "{ block-2 }\n";
        }
    }
}

// g++ -Wall -std=c++11 -Wno-unused-variable- -o with.exe with.cpp && with

// scoped(a)
// { block-1 }
// scoped(b)
// { block-2 }
// ~scoped(b)
// ~scoped(a)