BOOST_PP_FOR

The BOOST_PP_FOR macro represents a generalized horizontal repetition construct.

#### Usage

BOOST_PP_FOR(state, pred, op, macro)

#### Arguments

state
  The initial state.
pred
  A binary predicate of the form pred(r, state). This macro must expand to an integer in the range of 0 to BOOST_PP_LIMIT_MAG. BOOST_PP_FOR repeatedly expands macro while this predicate returns non-zero. This macro is called with the next available BOOST_PP_FOR repetition and the current state.
op
  A binary operation of the form op(r, state). This operation is expanded by BOOST_PP_FOR with the next available BOOST_PP_FOR repetition and the current state. This macro is repeatedly applied to the state, each time producing a new state, until pred returns 0.
macro
  A binary macro of the form macro(r, state). This macro is expanded by BOOST_PP_FOR with the next available BOOST_PP_FOR repetition and the current state. This macro is is repeated by BOOST_PP_FOR until pred returns 0.

#### Remarks

This macro expands to the sequence:
macro(r, state) macro(r, op(r, state)) ... macro(r, op(r, ... op(r, state) ... ))
The r value that is passed to pred, op, and macro represents the next available BOOST_PP_FOR repetition. Other macros that have _R suffix variants internally use BOOST_PP_FOR--for example, BOOST_PP_LIST_FOR_EACH and BOOST_PP_LIST_FOR_EACH_R. Using these _R versions is not strictly necessary, but passing the r value (that is passed to pred, op, and macro) to these macros allows them to reenter BOOST_PP_FOR with maximum efficiency.
To directly use this r value, rather than simply passing it to another macro, see BOOST_PP_FOR_r.
Previously, this macro could not be used recursively inside BOOST_PP_FOR. This limitation no longer exists, as the library can automatically detect the next available BOOST_PP_FOR repetition.

#### See Also

- BOOST_PP_FOR_r
- BOOST_PP_LIMIT_MAG

#### Requirements

Header: <boost/preprocessor/repetition/for.hpp>

#### Sample Code

    #include <boost/preprocessor/arithmetic/inc.hpp>
    #include <boost/preprocessor/comparison/not_equal.hpp>
    #include <boost/preprocessor/repetition/for.hpp>
    #include <boost/preprocessor/tuple/elem.hpp>

    #define PRED(r, state) \
       BOOST_PP_NOT_EQUAL( \
          BOOST_PP_TUPLE_ELEM(2, 0, state), \
          BOOST_PP_INC(BOOST_PP_TUPLE_ELEM(2, 1, state)) \
       ) \
       /**/

    #define OP(r, state) \
       ( \
          BOOST_PP_INC(BOOST_PP_TUPLE_ELEM(2, 0, state)), \
          BOOST_PP_TUPLE_ELEM(2, 1, state) \
       ) \
       /**/

    #define MACRO(r, state) BOOST_PP_TUPLE_ELEM(2, 0, state)

    BOOST_PP_FOR((5, 10), PRED, OP, MACRO) // expands to 5 6 7 8 9 10

© Copyright Housemarque Oy 2002 © Copyright Paul Mensonides 2002

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at www.boost.org/LICENSE_1_0.txt)