Re: [Boost-users] MPL to get rid of cumbersome switch

18 Mar 2006


      ...
Given its prepetitive nature you could use boost preprocessor library to
generate this switch...
...
::type);  \
          break;
      BOOST_PP_REPEAT(NUMBER_CASES, CASES, ~);
    }
That's a good idea.
I could define
#define NUMBER_CASES 4
and the switch would become something like that:
    switch(i)
    {
      #define CASES(z, n, text) 
\
        case n: 
\
          vec.push_back(new boost::mpl::at' token
C:/ventures/test/classes/main.cpp:47: error: `::value' has not been declared
C:/ventures/test/classes/main.cpp:47: error: `CASES' undeclared (first use 
this function)
C:/ventures/test/classes/main.cpp:47: error: expected primary-expression 
before ')' token
mingw32-make[1]: *** [release\main.o] Error 1

Any idea on how to make it work?
Many thanks
JCR
"Delfin Rojas"  wrote in message 
news:005001c64a19$6ed5c8e0$3000a8c0@winxpme...
...
...
John Christopher wrote:
Hello,
Still reading... Chapter 11 is still a few pages away...
Any way, I rewrote the program and I have something much simpler.
The vector of types has not changed:
    typedef boost::mpl::vector TTypes; but
the Functor has a new switch statement that is much easier to
maintain.
The nnumber of cases in the switch must be the number of
elements in the vector of types... Adding new cases is no big
deal anyway.
switch(i)
{
case 0:
    vec.push_back(new boost::mpl::at >::type);
    break;
case 1:
    vec.push_back(new boost::mpl::at >::type);
    break;
....
Given its prepetitive nature you could use boost preprocessor library to
generate this switch...
-delfin