this question also stems from compiler error generated in microsoft visual studio 2005 sp1 and microsof visual studio 2008. It compiles fine under cygwin and mingw. template <typename T> bool boost::pseudoprime(const T& n, const T& k) { typedef boost::operators<T> operatorT; BOOST_STATIC_ASSERT(is_integral<T>::value || (is_base_of::value)); // mingw says its k, microsoft complains about it. BOOST_ASSERT (n > T(2) && n % T(2) != 0); return modular_expo(k, n-1, n) != T(1) % n ? true : false; } Just trying to get a compiler work around. On 9/26/07, chun ping wang 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. Basically T is any integeral type or any class type that derives from boost::operators.

On 9/26/07, David Abrahams wrote:

...

on Wed Sep 26 2007, "chun ping wang" wrote:

...

template <typename T> bool boost::pseudoprime(const T& n, const T& k) { typedef boost::operators<T> operatorT; BOOST_STATIC_ASSERT(is_integral<T>::value); // static assert 1. BOOST_STATIC_ASSERT((is_base_of::value)); // static assert 2. BOOST_ASSERT (n > T(2) && n % T(2) != 0); return modular_expo(k, n-1, n) != T(1) % n ? true : false; }

now in vistual studio 2005 sp1 and visual studio 2008 beta the part "is_base_of::value" does not work if T happens to be an int or long due to "error C2803: 'operator --' must have at least one formal parameter of class type". I want to use enable_if to enable the STATIC_ASSERT only if T is NOT an arithmetic type for static assert 2.

enable_if can't "enable static asserts" in any sense that I understand. What are you really trying to do? Try to describe it without mentioning enable_if or STATIC_ASSERT. Just talk about the behavior you want.

-- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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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 wrote:

on Wed Sep 26 2007, "chun ping wang" 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?

-- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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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, return_type>::type // BitOperation.cpp line 44. namespace boost { // line 18 of MyOperators.hpp template char (& is_op_test(boost::operators 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 wrote:

on Mon Oct 01 2007, "chun ping wang" 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 char (& is_op_test(operators 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, return_type>::type f(T x) { ... }

-- Dave Abrahams Boost Consulting http://www.boost-consulting.com

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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 wrote:

the error was a missing semicolon after declaration of the array.

typename boost::enable_if, 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 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, return_type>::type // BitOperation.cpp line 44.

namespace boost { // line 18 of MyOperators.hpp template char (& is_op_test(boost::operators 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 wrote:

...

on Mon Oct 01 2007, "chun ping wang" 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 char (& is_op_test(operators 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, return_type>::type f(T x) { ... }

-- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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