[Boost-users] [preporcessor]Can we use BOOST_PP_SEQ_FOLD_LEFT on sequences with one element?

From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-07-10 17:59:14

Hello,

I'm a beginer with the preprocessor library. My goal is to generate from a 
sequence (a)(b)(c) => a::b::c and from (a) => a

I have tried with the following code

    #include <boost/preprocessor/seq/fold_left.hpp>
    #include <boost/preprocessor/seq/head.hpp>
    #include <boost/preprocessor/seq/tail.hpp>

    #define NAME(s, state, x) state::x

    BOOST_PP_SEQ_FOLD_LEFT(NAME, BOOST_PP_SEQ_HEAD((a)(b)), 
BOOST_PP_SEQ_TAIL((a)(b)))
    BOOST_PP_SEQ_FOLD_LEFT(NAME, BOOST_PP_SEQ_HEAD((a)), 
BOOST_PP_SEQ_TAIL((a)))

It works well with sequences with more than 1 element but with a sequence 
with only an element it fails, having the following preprocessor output 
(error?)

a::b
test.cpp:8:1: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 
given a::BOOST_PP_SEQ_ELEM_III

What I'm missing?

Thanks in advance,

Vicente