hey i got everything to work.. i realize after reading the doc return_type is the type you want to return.... On 10/3/07, chun ping wang <cablepuff@gmail.com> wrote:
the error was a missing semicolon after declaration of the array.
typename boost::enable_if<boost::mpl::or_<boost::is_arithmetic<T>, boost::is_operators<T> >, return_type>::type // line 44.
./cs512/c++/cppdef/BitOperation.cpp:44: error: 'return_type' was not declared in this scope ./cs512/c++/cppdef/BitOperation.cpp:44: error: template argument 2 is invalid ./cs512/c++/cppdef/BitOperation.cpp:45: error: expected initializer before 'Log2 '
On 10/3/07, chun ping wang <cablepuff@gmail.com> wrote:
hmm doesn't work. g++.exe -Wall -D__DEBUG__ -c ./cs512/c++/cppdef/BitOperation.cpp -o ./lib/BitOp eration.o -I"C:/Boost/include" -I"./bigint/c++" -fexceptions -fverbose-asm -f expensive-optimizations -O3 -pg -g3 ./cs512/c++/cppdef/../MyOperators.hpp:22: error: expected initializer before 'te mplate' ./cs512/c++/cppdef/BitOperation.cpp:44: error: 'return_type' was not declared in this scope ./cs512/c++/cppdef/BitOperation.cpp:44: error: template argument 2 is invalid ./cs512/c++/cppdef/BitOperation.cpp:45: error: expected initializer before 'Log2 ' ./cs512/c++/cppdef/BitOperation.cpp:151: error: 'return_type' was not declared i n this scope ./cs512/c++/cppdef/BitOperation.cpp:151: error: template argument 2 is invalid ./cs512/c++/cppdef/BitOperation.cpp:152: error: expected initializer before 'boo st'
heres the code .. typename boost::enable_if<boost::mpl::or_<boost::is_arithmetic<T>, boost::is_operators<T> >, return_type>::type // BitOperation.cpp line 44.
namespace boost { // line 18 of MyOperators.hpp template <class T, class U> char (& is_op_test(boost::operators<T,U> const&) )[2]
template <class T> char is_op_test(T const&); // line 24 of MyOperators.hpp }
I pass T as an int which should pass the first test.
On 10/1/07, David Abrahams <dave@boost-consulting.com> wrote:
on Mon Oct 01 2007, "chun ping wang" <cablepuff-AT-gmail.com> wrote:
hmm that is what i want for now... (i might change it later). I want to know to keept it in back of my head. Thanks.
On 10/1/07, David Abrahams < dave@boost-consulting.com> wrote:
on Wed Sep 26 2007, "chun ping wang" < cablepuff-AT-gmail.com > wrote:
> what i want to do is if type "T" happens to be a integeral type or a class type that inherits > from boost::operators than let the function compile otherwise a > compile time error appears.
I could tell you how, but it seems ill-advised. I really doubt you want to fail compilation if someone passes you a class type that acts just like int, but that isn't written using boost::operators. Are you sure that's what you want?
// untested template <class T, class U> char (& is_op_test(operators<T,U> const&) )[2]
template <class T> char is_op_test(T const&);
template<class T> T const& make();
template <class T> struct is_operators : mpl::bool_<(sizeof(is_op_test(make<T>())) == 2)> {};
template <class T> typename enable_if<mpl::or_<boost::is_integral<T>, is_operators<T> >, return_type>::type f(T x) { ... }
-- Dave Abrahams Boost Consulting http://www.boost-consulting.com
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