It looks like it's working find with gcc-2.95.3-5. One thing, though, it gave me a compiler error when I didn't #include <typeinfo>. Since you didn't list which header files you're including, I'm not sure if you're including <typeinfo> or not and what the Borland's behaviour would be if you didn't. Noel --- hicks <hicks@kgk.co.jp> wrote:
Hello
I have some questions for you: 1. Why are you so interested in the value of "typeid.name()"?
I'm not particulary interested in typeid::name() as an end result. As I said in the letter, I have real task at hand, and condensed the code so that anybody looking at it would be able to get to the point quickly. I used typeid()::name() here as a means of demonstating the problem. The result which is shown by typeid()::name() corresponds to the result encountered in the real task, namely, the next stage of processing is supposed to take place in traits1<int, 1> but takes place in traits1<int, 0> instead. In other words, the branching mechanism fails silently.
2. Are you sure this isn't a compiler problem? What compiler(s) have you tried this on?
Borland Builder C++ 5. Unfortunately, it's the only one to which I have access now. It could well be a compiler problem. Unless there are some rules which I don't understand. If it is a compiler problem perhaps someone knows of a workaround. I have tried various approaches to no avail.
Craig Hicks
Noel Yap wrote:
--- hicks <hicks@kgk.co.jp> <mailto:hicks@kgk.co.jp> wrote:
Query regarding the use/limitiations of traits in metaprogramming
I am trying to use traits pattern to assist in metaprogramming. I have the following problem.
A traits class "trait" defers a decision to another traits class "trait1" depending on the result of a third traits class "traita". However, the compiler does not cooperate. The code below excutes but gives unexpected output (also shown).
[Note:: The code has been reduced to the minimal to demonstrate the problem. I have a real task at hand not shown here.]
template <class T> struct traita { BOOST_STATIC_CONSTANT(int, value=0); }; template <> struct traita<int> { BOOST_STATIC_CONSTANT(int, value=1); };
template <class T, int> struct trait1 {};
template <class T> struct trait { BOOST_STATIC_CONSTANT(int, value=traita<T>::value); typedef trait1< ;T, value> t1; };
int main(int argc, char* argv[]) { std::cout << typeid(trait<int>::t1).name() << std::endl << trait<int>::value << std::endl ; return 0; }
output::
trait1<int,0> 1
It would be nice if the first line of output were "trait1<int, 1>", but it isn't.
Any assistance would be greatly appreciated.
I have some questions for you: 1. Why are you so interested in the value of "typeid.name()"? 2. Are you sure this isn't a compiler problem? What compiler(s) have you tried this on?
Noel
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