Re: variadic templates - compile error

From:
SG <s.gesemann@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 18 Aug 2011 21:56:32 -0700 (PDT)
Message-ID:
<0a56a3df-574a-4cab-88c1-ab718559163e@19g2000vbv.googlegroups.com>
On 19 Aug., 01:31, suresh <suresh.amritap...@gmail.com> wrote:

Hi,
Could you help me in fixing the compile error in the following code:

#include <sstream>
#include <iostream>

using namespace std;

template<typename T, typename ...P>
class Mystrcat{
public:
  Mystrcat(T t, P... p){init(t,p...);}
  ostringstream & get(){return o;}
private:
ostringstream o;
  void init(){}
  void init(T t, P... p);
};

template<typename T, typename ...P>
void Mystrcat<T,P...>::init(T t, P ...p){
  o << t;
  if (sizeof...(p)) init(p...);
}

int main(){
  Mystrcat<char*,char *> m("Amma","Namasivayah");
  cout << m.get().str();
}

I get the error, no matching function for call to =91Mystrcat<char*, char=

*>::init(char*&)'

Your Mystrcat<char*,char*> ohly has two init functions:
- void init()
- void init(char*,char*)

and inside the second one, you're trying to call some nonexistinc init
with just a single parameter.

Also, I fail to see the benefit of a class here. Why not simply:

  inline void strcat_helper(ostream & os) {} // nothing to do

  template<class T, class... More>
  inline void strcat_helper(ostream & os, T && t, More &&... more)
  {
    os << forward<T>(t);
    strcat_helper(os,forward<More>(more)...);
  }

  template<class... Args>
  string strcat(Args &&... args)
  {
    ostringstream os;
    strcat_helper(os,forward<Args>(args)...);
    return os.str();
  }

SG

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