> I have a question related to enable_if. I would like to enable or
> disable
> some member functions from a template class, but enable_if is -not
> enable-
> to do it :-)

> Here is the code.

> template <class T>
> class A
> {
> ...
>       enable_if< boost::is_arithmetic<T>, void > :: type  f1()
>       {
>             ...
>       }
> };

> In class A, I want to define function f1 only if the template
> parameter is
> arithmetic. It works fine except when the parameter is not arithmetic.
> I
> have a compile error "error C2039: 'type' : is not a member of
> 'boost::enable_if<Cond,T>'" (Working with VC7.1, and boost 3.12)

> Thank you in advance for any suggestions and help.

> Sincerely yours,

> Yutaka Leon Suematsu

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

> A a;
> a.f1<int>();

> The problem is that T is not a template parameter of you function f1.
> It is a template parameter of the class A. So when the class A
> is instantiated with some type that is not arithmetic, say void*,
> it is as if you would directly write a function:

> enable_if<boost::is_arithmetic<void*>, void>::type

> which is

> enable_if<false, void>::type

> which is an error, since enable_if<false,void> is an empty class.

> You can write your code as follows to make enable_if work, but it may
> not be a solution that works:

> class A
> {
> ...
>        template <class T>
>        enable_if< boost::is_arithmetic<T>, void > :: type  f1()
>        {
>              ...
>        }
> };

> Also, here you need to explicitly instantiate f1 as

> A a;

> a.f1<int>();

> Best, Jaakko Järvi

> On Apr 1, 2005, at 3:27 AM, Yutaka Leon Suematsu wrote:

>> Dear booster,

>> I have a question related to enable_if. I would like to enable or
>> disable
>> some member functions from a template class, but enable_if is -not
>> enable-
>> to do it :-)

>> Here is the code.

>> template <class T>
>> class A
>> {
>> ...
>>       enable_if< boost::is_arithmetic<T>, void > :: type  f1()
>>       {
>>             ...
>>       }
>> };

>> In class A, I want to define function f1 only if the template
>> parameter is
>> arithmetic. It works fine except when the parameter is not
>> arithmetic. I
>> have a compile error "error C2039: 'type' : is not a member of
>> 'boost::enable_if<Cond,T>'" (Working with VC7.1, and boost 3.12)

>> Thank you in advance for any suggestions and help.

>> Sincerely yours,

>> Yutaka Leon Suematsu

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

> -- Jaakko Järvi, Assistant Professor
> -- Texas A&M University, Computer Science
> -- ja...@cs.tamu.edu

> I have a question related to enable_if. I would like to enable or
> disable some member functions from a template class, but enable_if is
> -not enable- to do it :-)

> So, instead  to use a regex like this:

> "\s*(\d+)\s+(\d+)\s+(\d+)\s+"

> I would like to be able to use something like:

> "\s*([$VALUE1]\d+)\s+([$VALUE2]\d+)\s+([$VALUE3]\d+)\s+"

> I don't know if this feature exists in regex but I haven't found it but
> maybe I dind't know where to find...

> No that's not supported, but don't forget that you can always use
> non-marking parenthesis to avoid throwing out too many fields.

> John.

> > No that's not supported, but don't forget that you can always use
> > non-marking parenthesis to avoid throwing out too many fields.

> > John.

> I already use non-marking parenthesis but when using a long regex it's
> very difficult to decide which is the correct index to define the
> subexpression to use.  Furthermore, when using "conditional
> expressiones" in the format strings the difficulties are even more
> obvious...

> Thanks anyway for your reply,

> Jordi

> > Jordi - something like Regex Coach (http://www.weitz.de/regex-coach/)
> > makes it a lot easier to work out what match indices to use for the
> > different captures in your regular expressions...

> I'm already using Regex Coach because someone in this group suggested it
> to check my regex.  I think it's a very great tool!.

> I have just realized there is the option to get the index in the
> "Hightlight" section but I don't know how to get an index greater than
> 10... (anyone knows how to do that?)

> Thanks,

> Jordi

> No that's not supported, but don't forget that you can always use
> non-marking parenthesis to avoid throwing out too many fields.

> John.