preprocessor bug

From: jkharris01 (john.harris_at_[hidden])
Date: 2002-04-04 16:43:41

Using MSVC6, SP5:

BOOST_PP_LIST_AT() doesn't work in a transform function, but BOOST_PP_LIST_FIRST() and BOOST_PP_LIST_REST() work fine

I expected the following code to expand to:

    a , b
but instead it expands to

 BOOST_PP_TUPLE3_ELEM0 BOOST_PP_TUPLE2_ELEM0 BOOST_PP_WHILE0(BOOST_PP_LIST_REST_N_C,BOOST_PP_LIST_REST_N_F,((a,(7,(_,_,0),1),1),0)) , BOOST_PP_TUPLE3_ELEM0 BOOST_PP_TUPLE2_ELEM0 BOOST_PP_WHILE0(BOOST_PP_LIST_REST_N_C,BOOST_PP_LIST_REST_N_F,((b,(8,(_,_,0),1),1),0))

If I change the definition of F to use BOOST_PP_FIRST(X), it works

************* Example code***************

#define F(a,b,X) BOOST_PP_LIST_AT(X,0)
#define LST BOOST_PP_TUPLE_TO_LIST(2,( \
  BOOST_PP_TUPLE_TO_LIST(2,(a,7)), \
  BOOST_PP_TUPLE_TO_LIST(2,(b,8))))

BOOST_PP_LIST_ENUM(BOOST_PP_LIST_TRANSFORM(F,dummy,LST))