TITLE: returning multiple values 

(Source: comp.lang.c++, 27 Jan 2001)

WAHLER: Mike Wahler (mkwahler@ix.netcom.com)

>: In C++, a function can return only one value.

KUEHL: "Dietmar Kuehl" <kuehl@ramsen.informatik.uni-konstanz.de>

... which, of course, can be a composite of two values.

WAHLER:

>: #include <iostream>
>:
>: void getFraction(int x, int y, int& result1, int&result2)
>: {
>:     result1 = x * x;
>:     result2 = y * y;
>: }

KUEHL:

 ... or use something like this:

   std::pair<int, int> getFraction(int x, int y)
   {
     return std::make_pair(x * x, y * y);
   }

 ... and with a little helper do this:

   template <typename T1, typename T2>
   struct binder_t {
     binder_t(T1& v1, T2& v2): r1(v1), r2(v2) {}
     template <typename S1, typename S2>
     void operator= (std::pair<S1, S2> const& p) {
       r1 = p.first;
       r2 = p.second;
     }
   private:
     T1& r1;
     T2& r2;
   };

   template <typename T1, typename T2>
   binder_t<T1, T2> binder(T1& r1, T2& r2) {
     return binder_t<T1, T2>(r1, r2);
   }

   int main()
   {
     int r1;
     int r2;
     binder(r1, r2) = getFraction(2, 4);
     std::cout << "r1 = " << r1 << "\n";
     std::cout << "r2 = " << r2 << "\n";
   }



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