There should be no problems using this macro in a header file. I get around the one definition rule by simply making the enum actually be a namespace with static functions inside that namespace. So basically: BOOST_ENUM(Foo, (a)(b)) expands into: namespace Foo { enum type { a, b, size = 2, Invalid = -1 }; typedef boost::array<const std::string, size+1> array_type; static const array_type names = { "a", "b", "2" }; static const std::string& str(type index) { assert(index >= 0 && index <= size); return names[(int)index]; } static bool parse(const std::string& str, type& value) { array_type::const_iterator it = std::find(names.begin(), names.end(), str); if(it == names.end()) return false; value = (type)(it - names.begin()); return true; } static std::ostream& operator << (std::ostream& os, type value) { os << str(value); return os; } } On 12/7/05, Martin Bonner <martin.bonner@pitechnology.com> wrote:
----Original Message---- From: Frank Laub [mailto:frank.laub@gmail.com] Sent: 07 December 2005 11:47 To: boost@lists.boost.org Subject: [boost] BOOST_ENUM proposal
Hello fellow boosters,
I've recently come up with a way to use the boost preprocesor to generate a 'better' enum type. The following is an example of some typical usage. Is anyone else interested in this sort of thing?
**YES**!!
I'm hoping to get suggestions for how to make it more 'boost-like' in both its implementation and its usage. Is this very readable? Is there a place I can upload the code for people to peruse?
#include <iostream> #include <boost/enum.hpp> #include <boost/foreach.hpp> #define foreach BOOST_FOREACH I hope that this line is just needed for the demo code in main.
BOOST_ENUM(Level, (Abort)("unrecoverable problem") (Error)("recoverable problem") (Alert)("unexpected behavior") (Info)("expected behavior") (Trace)("normal flow of execution") (Debug)("detailed object state listings") )
Now we come to the meat of the problem. Here you have defined 'Level' at directly in a cpp file. Normally, I would want to define an enum in a header file, and I see potential problems with violations of the one-definition-rule.
Also: does your implementation cope with defining an enum inside a class? (I could live with an answer of "No" - I would just have to put the enum outside the class.)
Is your implementation limited to 255 elements (normal boost preprocessor limit)?
Can I specify enum values (ie Abort=0, Info=16)?
int main() { foreach(const string& name, Level::names) { cout << name << endl; } cout << "1: " << Level::names[1] << endl; cout << "toString(Abort): " << Level::toString(Level::Abort) << endl; cout << "getValue(Abort): " << Level::getValue(Level::Abort) << endl;
Level::type value = Level::Invalid; bool ret = Level::fromString("Abort", value); cout << "fromString(\"Abort\"): " << ret << ", " << value << endl;
value = Level::Invalid; ret = Level::fromString("Debug", value); cout << "fromString(\"Debug\"): " << ret << ", " << value << endl;
value = Level::Invalid; ret = Level::fromString("not in enum", value); cout << "fromString(\"not in enum\"): " << ret << ", " << value << endl;
return 0; }
With the program output being:
Abort Error Alert Info Trace Debug Invalid 1: Error toString(Abort): Abort getValue(Abort): unrecoverable problem fromString("Abort"): 1, 0 fromString("Debug"): 1, 5 fromString("not in enum"): 0, 6
-Frank
-- Martin Bonner Martin.Bonner@Pitechnology.com Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ, ENGLAND Tel: +44 (0)1223 441434 _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost