Preprocessor library: inrement a macro
Hello, I simply want to increment a macro, like that: #define VARIABLE 7 FunctionA( VARIABLE ); // VARIABLE expands to 7 #define VARIABLE BOOST_PP_INC(VARIABLE) FunctionB( VARIABLE ); // VARIABLE expands to 8 #define VARIABLE BOOST_PP_INC(VARIABLE) FunctionC( VARIABLE ); // VARIABLE expands to 9 #define VARIABLE BOOST_PP_INC(VARIABLE) ... Of course, as I have written it, it does not work. What's the right way? Thanks a lot! Arno P.S. I don't want to iterate. FunctionA/B/C are all different constructs. I simply want to avoid forgetting to adjust all numbers when making a change to the chain of calls.
-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Arno Schödl
I simply want to increment a macro, like that:
#define VARIABLE 7 FunctionA( VARIABLE ); // VARIABLE expands to 7 #define VARIABLE BOOST_PP_INC(VARIABLE) FunctionB( VARIABLE ); // VARIABLE expands to 8 #define VARIABLE BOOST_PP_INC(VARIABLE) FunctionC( VARIABLE ); // VARIABLE expands to 9 #define VARIABLE BOOST_PP_INC(VARIABLE) ...
Of course, as I have written it, it does not work. What's the right way?
The closest mechanism in the pp-lib is the slot mechanism. E.g. #include <boost/preprocessor/slot/slot.hpp> #define BOOST_PP_VALUE 7 #include BOOST_PP_ASSIGN_SLOT(1) FunctionA( BOOST_PP_SLOT(1) ); // BOOST_PP_SLOT(1) expands to 7 #define BOOST_PP_VALUE BOOST_PP_SLOT(1) + 1 #include BOOST_PP_ASSIGN_SLOT(1) FunctionB( BOOST_PP_SLOT(1) ); // BOOST_PP_SLOT(1) expands to 8 #define BOOST_PP_VALUE BOOST_PP_SLOT(1) + 1 #include BOOST_PP_ASSIGN_SLOT(1) FunctionC( BOOST_PP_SLOT(1) ); // BOOST_PP_SLOT(1) expands to 9 This can be condensed somewhat: // ----- variable.hpp ----- // #ifndef VARIABLE_HPP #define VARIABLE_HPP #include <boost/preprocessor/slot/slot.hpp> #define BOOST_PP_VALUE 7 #include BOOST_PP_ASSIGN_SLOT(1) #define VARIABLE BOOST_PP_SLOT(1) #define INC_VARIABLE() "inc_variable.hpp" #endif // ----- inc_variable.hpp ----- // #define BOOST_PP_VALUE VARIABLE + 1 #include BOOST_PP_ASSIGN_SLOT(1) // ----- client.cpp ----- // #include "variable.hpp" FunctionA( VARIABLE ); #include INC_VARIABLE() FunctionB( VARIABLE ); #include INC_VARIABLE() FunctionC( VARIABLE ); That is about the best you can do. Regards, Paul Mensonides
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Arno Schödl -
Paul Mensonides