The BOOST_PP_ITERATION_DEPTH macro expands to the current file-iteration depth.

#### Usage

BOOST_PP_ITERATION_DEPTH()

#### Remarks

If a file-iteration is not in progress, this macro expands to 0. Otherwise, it expands to the current depth of file-iteration.

#### Requirements

Header: <boost/preprocessor/iteration/iterate.hpp>

#### Sample Code

    // file.h
    #if !BOOST_PP_IS_ITERATING

       #ifndef FILE_H_
       #define FILE_H_

       #include <boost/preprocessor/iteration/iterate.hpp>

       #define BOOST_PP_ITERATION_PARAMS_1 (3, (1, 3, "file.h"))
       #include BOOST_PP_ITERATE()

       #endif

    #elif BOOST_PP_ITERATION_DEPTH() == 1

       + depth BOOST_PP_ITERATION_DEPTH()
       // ...

       #define BOOST_PP_ITERATION_PARAMS_2 /* ... */ \
          (3, (1, BOOST_PP_ITERATION(), "file.h"))   \
          /**/

       #include BOOST_PP_ITERATE()

    #elif BOOST_PP_ITERATION_DEPTH() == 2

       - depth BOOST_PP_ITERATION_DEPTH()
       // ...

    #endif