Re: template with STL container

softwareEngineer <>
Fri, 07 Oct 2011 10:42:01 +0200
Il 05/10/2011 21:08, Paul <pchrist ha scritto:

"Nobody"<> wrote in message

On Tue, 04 Oct 2011 16:16:00 +0200, softwareEngineer wrote:

Yes, but I need a vector of generic value (float, int, ecc.)

In which case, the values need a common base class, e.g.:

class MY_Value {

template<typename T>
class MY_Value_T : public MY_Value {

std::vector<MY_Value*> v;

MyValue_T<int> iV1 = 1;
MyValue_T<float> iV2 = 2.1;
v[0] = static_cast<MY_Value*>(&iV1);
v[1] = static_cast<MY_Value*>(&iV2);

Casting the vector elements back to their correct type is a bit more
involved, as you need to know what their correct type is, either by
using RTTI or by explicitly adding a tag field to the base class.

You can do this kind of thing if you have a limited set of different types:

template<class T1=float, class T2=int, class T3=std::string>
class Base{
  virtual operator T1(){return 0;}
  virtual operator T2(){return 0;}
  virtual operator T3(){return 0;}

template<class T, class T1=float, class T2=int, class T3=std::string>
class Derived:public Base<T1,T2,T3>{
  T itsData;
  Derived(T x):itsData(x){};
  virtual operator T(){return itsData;}

  Derived<float> d1(-4.0/3.0);
  Derived<std::string> d2("Hello");

  std::vector< Base<>*> v1;
  float f1 = *v1[0];
  v1[0] =&d2;
  std::string s1= *v1[0];

Its more difficult if you want unlimited amount of different types.

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