It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example: http://pastebin.com/mH2cZ4NP I wonder if has_member_fnc would be a good addition to boost?
Neal Becker wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wish I could see the code, but pastebin is blocked here.
I wonder if has_member_fnc would be a good addition to boost?
has_member_function would be a good addition, assuming it works. _____ Rob Stewart robert.stewart@sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.
On Fri, Mar 16, 2012 at 4:07 PM, Stewart, Robert <Robert.Stewart@sig.com> wrote:
Neal Becker wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wish I could see the code, but pastebin is blocked here.
template <typename T> //Special template for EE_PDUs, which are weird auto getKey_imp(const T &struc, int &key, int) -> decltype(struc.interesting_member, void()) //If struc has an interesting_member member, this version is used { key = 0; } template <typename T> void getKey_imp(const T &struc, int &key, long) //struc didn't have an interesting_member member, do nothing { } public: template <typename T> bool getKey(const T &struc, int &key) { getKey_imp(struc, key, 0); return key == 0; //Successful? } -- Olaf
Olaf van der Spek wrote:
On Fri, Mar 16, 2012 at 4:07 PM, Stewart, Robert <Robert.Stewart@sig.com> wrote:
Neal Becker wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wish I could see the code, but pastebin is blocked here.
//Special template for EE_PDUs, which are weird template <typename T> auto getKey_imp(const T &struc, int &key, int) -> //If struc has an interesting_member member, this //version is used decltype(struc.interesting_member, void()) { key = 0; } template <typename T> void getKey_imp(const T &struc, int &key, long) //struc didn't have an interesting_member member, do //nothing { }
public: template <typename T> bool getKey(const T &struc, int &key) { getKey_imp(struc, key, 0); return key == 0; //Successful? }
Thank you. Did I miss something? That just tests for a member by name. To test for a member function, you'd need to specify the signature to make it worthwhile. _____ Rob Stewart robert.stewart@sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.
________________________________ From: "Stewart, Robert" <Robert.Stewart@sig.com> To: "boost@lists.boost.org" <boost@lists.boost.org> Sent: Friday, March 16, 2012 2:29 PM Subject: Re: [boost] has_member_fnc?
Olaf van der Spek wrote:
On Fri, Mar 16, 2012 at 4:07 PM, Stewart, Robert <Robert.Stewart@sig.com> wrote:
Neal Becker wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wish I could see the code, but pastebin is blocked here.
//Special template for EE_PDUs, which are weird template <typename T> auto getKey_imp(const T &struc, int &key, int) -> //If struc has an interesting_member member, this //version is used decltype(struc.interesting_member, void()) { key = 0; } template <typename T> void getKey_imp(const T &struc, int &key, long) //struc didn't have an interesting_member member, do //nothing { }
public: template <typename T> bool getKey(const T &struc, int &key) { getKey_imp(struc, key, 0); return key == 0; //Successful? }
Thank you.
Did I miss something? That just tests for a member by name. To test for a member function, you'd need to specify the signature to make it worthwhile.
In C++11, SFINAE was extended to work for expressions also. So this will work on compilers that support it(which MSVC does not). Using an expression is much better that the signature because this will work on template members, and it disambiguates better.
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function? Or is what you had in mind something different? Regards, Nate
Nathan Ridge wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function?
Or is what you had in mind something different?
Regards, Nate
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
What is the status of TTI? I don't see it in 1.49.0.
On 3/16/2012 2:15 PM, Neal Becker wrote:
Nathan Ridge wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function?
Or is what you had in mind something different?
Regards, Nate
_______________________________________________ Unsubscribe& other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
What is the status of TTI? I don't see it in 1.49.0.
This is my fault. I have not had the chance of working on TTI to get it into an upcoming Boost release. I will be working on it more so I hope to get it into a Boost release in the near future. Apologies to all about this. Eddie Diener
On 3/16/2012 2:15 PM, Neal Becker wrote:
Nathan Ridge wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function?
Or is what you had in mind something different?
Regards, Nate
_______________________________________________ Unsubscribe& other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
What is the status of TTI? I don't see it in 1.49.0.
This is my fault. I have not had the chance of working on TTI to get it into an upcoming Boost release. I will be working on it more so I hope to get it into a Boost release in the near future. Apologies to all about this. Eddie Diener
On 3/16/2012 2:15 PM, Neal Becker wrote:
Nathan Ridge wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function?
Or is what you had in mind something different?
Regards, Nate
_______________________________________________ Unsubscribe& other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
What is the status of TTI? I don't see it in 1.49.0.
This is my fault. I have not had the chance of working on TTI to get it into an upcoming Boost release. I will be working on it more so I hope to get it into a Boost release in the near future. Apologies to all about this. Eddie Diener
On 3/16/2012 12:28 PM, Nathan Ridge wrote:
It seems c++11 has a new way to spell enable_if, and this can be used to implement has_member_fnc, as in this example:
I wonder if has_member_fnc would be a good addition to boost?
Does Boost.TTI not already have a facility to test for the existence of a member function?
Yes, TTI does have this facility, generated by a macro. But using C++11 features is definitely an improvement when the compiler supports it. I need to look at C++11 more closely as I work to get TTI ready for Boost. Eddie Diener
participants (6)
-
Edward Diener -
Nathan Ridge -
Neal Becker -
Olaf van der Spek -
paul Fultz -
Stewart, Robert