Re: [Boost-users] [Preprocessor] how to use REPEAT_FROM_TO for 2 arguments

7 Jan 2010

      Hi Steven,

thanks for your answer. It solves my puzzle.

BR,

/Kenny

2010/1/6 Steven Watanabe 
...
AMDG
Kai Liu wrote:
...
I am trying to use the preprocessor library to simplify the code I have.
The problem:
I have many lines of the following assignments:
mybfclass x_0_mybf;
mybfclass x_1_mybf;
...
mybfclass1 x_0_mybf1;
mybfclass1 x_1_mybf1;
...
mybfclass2 x_0_mybf2;
mybfclass2 x_1_mybf2;
then I defined several vectors:
vector x_mybf;
vector x_mybf1;
vector x_mybf2;
*
use the boost preprocessor library, I write the following code:
#define* DECLX_mybf(z, n, text) BOOST_PP_CAT(text, BOOST_PP_CAT(_,
mybf)).push_back(&BOOST_PP_CAT(text, BOOST_PP_CAT(BOOST_PP_CAT(_, n),
BOOST_PP_CAT(_, mybf))));
*#define* DECLX_mybf1(z, n, text) BOOST_PP_CAT(text, BOOST_PP_CAT(_,
mybf)).push_back(&BOOST_PP_CAT(text, BOOST_PP_CAT(BOOST_PP_CAT(_, n),
BOOST_PP_CAT(_, mybf))));
*#define* DECLX_mybf2(z, n, text) BOOST_PP_CAT(text, BOOST_PP_CAT(_,
mybf)).push_back(&BOOST_PP_CAT(text, BOOST_PP_CAT(BOOST_PP_CAT(_, n),
BOOST_PP_CAT(_, mybf))));
BOOST_PP_REPEAT_FROM_TO(0, 2, DECLX_mybf, x);
*// generated: x_mybf.push_back(&x_0_mybf); x_mybf.push_back(&x_1_mybf);
* BOOST_PP_REPEAT_FROM_TO(0, 2, DECLX_mybf1, x);
*// generated: x_mybf1.push_back(&x_0_mybf1);
x_mybf1.push_back(&x_1_mybf);
* BOOST_PP_REPEAT_FROM_TO(0, 2, DECLX_mybf2, x);
*// generated: x_mybf2.push_back(&x_0_mybf2);
x_mybf2.push_back(&x_1_mybf);
*
but I think it is too much coding here, since I have to write a macro for
each mybf occurrence, DECLX_mybf
I have difficulty to use the BOOST_PP_REPEAT_FROM_TO for two argument,
since
the macro(z, x, data) can only accept one argument data, however, I need
to
pass two arguments x and mybf to the macro,
in order to generate a mybfclass1 x_0_mybf.
does anyone know how to apply macro to generate the above structure?
Wrap the arguments in a tuple:
#define DECLX(z, n, data) \
  BOOST_PP_CAT(\
      BOOST_PP_TUPLE_ELEM(2, 1, data),\
      BOOST_PP_CAT(\
          _,\
          BOOST_PP_TUPLE_ELEM(2, 0, data))\
  ).push_back(\
      &BOOST_PP_CAT(\
          BOOST_PP_TUPLE_ELEM(2, 1, data),\
BOOST_PP_CAT(\
              BOOST_PP_CAT(_, n),\
              BOOST_PP_CAT(\
                  _,\
                  BOOST_PP_TUPLE_ELEM(2, 0, data)))));
BOOST_PP_REPEAT_FROM_TO(0, 2, DECLX, (mybf, x));
In Christ,
Steven Watanabe
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Kai Liu
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91052, Erlangen
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