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From: maverick on 20 Dec 2009 21:54 Hi, I have a legacy code: template<Uint64 BuffLenT> Struct UNum : BasicTypes<BuffLenT> { typedef Uint64 NumberT; inline NumberT operator() () const { NumberT ret = 0; sscanf (this->buffer_, "%ul", &ret); return ret; } }; Uint64 is a typedef and comes from "internal" headers. It may gets defined to unsigned long or unsigned long long (depending upon situations). Therefore to handle the situation I want to do the following: template<> Struct UNum<unsigned long long BuffLenT> : BasicTypes<BuffLenT> { typedef Uint64 NumberT; inline NumberT operator() () const { NumberT ret = 0; sscanf (this->buffer_, "%ull", &ret); return ret; } }; But this results in an compilation error. Any help in this regard will be much appreciated. Thanks in advance -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Chris Uzdavinis on 21 Dec 2009 07:19 On Dec 21, 8:54 am, maverick <mod...(a)gmail.com> wrote: > Uint64 is a typedef and comes from "internal" headers. It may gets > defined to unsigned long or unsigned long long (depending upon > situations). Therefore to handle the situation I want to do the > following: > > template<> Struct UNum<unsigned long long BuffLenT> : > BasicTypes<BuffLenT> > { > typedef Uint64 NumberT; > inline NumberT operator() () const > { > > NumberT ret = 0; > sscanf (this->buffer_, "%ull", &ret); > return ret; > } > > }; > > But this results in an compilation error. Any help in this regard will > be much appreciated. If the format string is all that you need to vary with the type, then factor it out: template <typename T> char const * formatString(); template<> char const * formatString<unsigned long>() { return "%ul"; } template<> char const * formatString<unsigned long long>() { return "%ull"; } // ... other types omitted Then, to use it: sscanf (this->buffer_, formatString<NumberT>(), &ret); If you don't mind passing unused values, you could even get rid of the templates and just use traditional function overloading: char const * formatString(unsigned long) { return "%ul"; } char const * formatString(unsigned long long) { return "%ull"; } // ... other types omitted sscanf (this->buffer_, formatString(ret), &ret); Hope this helps. Chris -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: 萌 朱 on 21 Dec 2009 07:20 On Dec 21, 9:54 am, maverick <mod...(a)gmail.com> wrote: > Hi, > > I have a legacy code: > > template<Uint64 BuffLenT> Struct UNum : BasicTypes<BuffLenT> > { > typedef Uint64 NumberT; > inline NumberT operator() () const > { > > NumberT ret = 0; > sscanf (this->buffer_, "%ul", &ret); > return ret; > } > > }; > > Uint64 is a typedef and comes from "internal" headers. It may gets > defined to unsigned long or unsigned long long (depending upon > situations). Therefore to handle the situation I want to do the > following: > > template<> Struct UNum<unsigned long long BuffLenT> : > BasicTypes<BuffLenT> > { > typedef Uint64 NumberT; > inline NumberT operator() () const > { > > NumberT ret = 0; > sscanf (this->buffer_, "%ull", &ret); > return ret; > } > > }; > > But this results in an compilation error. Any help in this regard will > be much appreciated. > > Thanks in advance > > -- > [ Seehttp://www.gotw.ca/resources/clcm.htmfor info about ] > [ comp.lang.c++.moderated. First time posters: Do this! ] I suggest you do something like this. // Primary template, everything else falls into here template <typename> struct UNum; // Specialization for unsigned long template <> struct UNum <unsigned long> : BasicTypes<unsigned long> { typedef unsigned long NumberT; inline NumberT operator() () const { // Special process for unsigned long } }; // Specialization for unsigned long long template <> struct UNum <unsigned long long> : BasicTypes<unsigned long long> { typedef unsigned long long NumberT; inline NumberT operator() () const { // Special process for unsigned long long } }; If you design it this way, you will get what you want for unsigned long and unsigned long long. The primary template is intentionally left invalid so that everything else falls into it and generates compiler errors which will surely catch your attention. Therefore, you will never have a struct UNum <float> goes unnoticed which might what you want or do not want. In case you want general cases are addressed in a third way, you can give definition for the primary template. -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Thomas Maeder on 21 Dec 2009 07:25 maverick <modwel(a)gmail.com> writes: > Uint64 is a typedef and comes from "internal" headers. It may gets > defined to unsigned long or unsigned long long (depending upon > situations). What does Uint64 name in the compiler run that produces the error you mention? > But this results in an compilation error. Please copy&paste the error message(s). -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: something_fit on 21 Dec 2009 12:18
On Dec 21, 2:54 pm, maverick <mod...(a)gmail.com> wrote: > Hi, > > I have a legacy code: > > template<Uint64 BuffLenT> Struct UNum : BasicTypes<BuffLenT> > { > typedef Uint64 NumberT; > inline NumberT operator() () const > { > > NumberT ret = 0; > sscanf (this->buffer_, "%ul", &ret); > return ret; > } > > }; > > Uint64 is a typedef and comes from "internal" headers. It may gets > defined to unsigned long or unsigned long long (depending upon > situations). Therefore to handle the situation I want to do the > following: > > template<> Struct UNum<unsigned long long BuffLenT> : > BasicTypes<BuffLenT> > { > typedef Uint64 NumberT; > inline NumberT operator() () const > { > > NumberT ret = 0; > sscanf (this->buffer_, "%ull", &ret); > return ret; > } > > }; > > But this results in an compilation error. Any help in this regard will > be much appreciated. > > Thanks in advance > > -- > [ Seehttp://www.gotw.ca/resources/clcm.htmfor info about ] > [ comp.lang.c++.moderated. First time posters: Do this! ] BuffLenT isn't a type, it's a value, so theres no intermediate information there about it's type -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |