The BOOST_PP_COMMA_IF macro conditionally expands to a comma.

#### Usage

BOOST_PP_COMMA_IF(cond)

#### Arguments

cond
  The condition that determines if a the macro expands to a comma or nothing. Valid values range from 0 to BOOST_PP_LIMIT_MAG.

#### Remarks

If cond expands to 0, this macro expands to nothing. Otherwise, it expands to a comma.
The preprocessor interprets commas as argument separators in macro invocations. Because of this, commas require special handling.

#### See Also

- BOOST_PP_LIMIT_MAG

#### Requirements

Header: <boost/preprocessor/punctuation/comma_if.hpp>

#### Sample Code

    #include <boost/preprocessor/punctuation/comma_if.hpp>
    #include <boost/preprocessor/repetition/repeat.hpp>

    #define MACRO(z, n, text) BOOST_PP_COMMA_IF(n) text

    BOOST_PP_REPEAT(3, MACRO, class) // expands to class, class, class