id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
5578,non-mutable local variables in phoenix,anonymous,Thomas Heller,"Phoenix local variables are non-mutable with the test case below. It seems like making a local variable non-mutable in these cases is the wrong thing to do.

If you follow my logic:
  * TEST1 -- the local is a ref to the variable i
  * TEST2 -- the local is an int containing the value from arg1 or i (and is mutable)
  * TEST3 -- I would ''expect'' the local to be an into containing the value from arg1... but it doesn't compile because it things the local is immutable
  * TEST4 -- I would ''expect'' this to work the same as TEST3


{{{
#!cpp
#define TEST3

#include <iostream>
#include <boost/phoenix/phoenix.hpp>

int main()
{
   using namespace boost::phoenix;
   using namespace boost::phoenix::arg_names;
   using namespace boost::phoenix::local_names;


#ifdef TEST1
   std::cout << ""TEST1"" << std::endl;
   /**
    *   This will print 41 41.
    *   _a is a local variable that is a reference to i. This is a little surprising
    *   at first but not too bad. We can deal with it.
    */
   int i = 42;
   let( _a = arg1 )
   [
      std::cout << --_a
   ](i);

   std::cout << ' ' << i << std::endl;

#endif // TEST1


#ifdef TEST2
   std::cout << ""TEST2"" << std::endl;
   /**
    *   This will print 41 42.
    *   _a is a local variable initialized with the value of arg1. Makes sense
    */
   int i = 42;
   let( _a = val(arg1) )
   [
      std::cout << --_a
   ](i);

   std::cout << ' ' << i << std::endl;

#endif // TEST2



#ifdef TEST3
   std::cout << ""TEST3"" << std::endl;
   /**
    *   This wont compile because _a is not mutable. This is not only
    *   surprising but makes local scoped variables have very limited use.
    */
   let( _a = val(arg1) )
   [
      std::cout << --_a
   ](42);

#endif // TEST3



#ifdef TEST4
   std::cout << ""TEST4"" << std::endl;
   /**
    *   This fails for the same reason... I would expect it to work also.
    */
   let( _a = val(42) )
   [
      std::cout << --_a
   ]();

#endif // TEST4


   return 1;
} 

}}}
",Bugs,closed,Boost 1.47.0,phoenix,Boost 1.46.1,Problem,worksforme,,