CODEWITHSUNDEEP
c++ooptemplates
Rog Matthews
Rog Matthews

Reputation: 3247

Error in c++ template Snippet

I hae written the following code:

class Object
{
   public:
   Object()
   {}
};

template <class T>
class Reg : public Object
{
    T val,val_new;
    public:
    Reg(T initval)
    {
    super( );
    val=initval;
    } 
};

The error in the code is

t.cpp: In constructor 'Reg<T>::Reg(T)':
Line 15: error: there are no arguments to 'super' that depend on a template parameter,
so a declaration of 'super' must be available
compilation terminated due to -Wfatal-errors.

How can i eliminate the error?

Upvotes: 0

Views: 121

Answers (2)

Cheers and hth. - Alf
Cheers and hth. - Alf

Reputation: 145389

class Object
{
public:
   Object() {}
};

template <class T>
class Reg : public Object
{
    T val,val_new;
public:
    Reg(T const& initval)
        : val( initval )
    {} 
};

There is no super in standard C++. Some compilers offer it as a language extension, but in standard C++ if you want a generic name for “the” base class, then you have to typedef it. For example, in class Reg you can typedef Object Base;.

The construction : val( initval ) is a constructor initializer list, where essentially you call constructors of members and base classes, avoiding default construction.

Finally, the const&, passing by reference, avoids time-consuming and memory-consuming copying of the actual argument; it's another thing that's different in C++ (compared to Java, which I’m assuming that you’re coming from).

Upvotes: 5

Anycorn
Anycorn

Reputation: 51525

class Object
{
   public:
   Object()
   {}
};

template <class T>
class Reg : public Object
{
    T val,val_new;
    public:
    Reg(T initval) : Object() // initializer list
    {
    val=initval;
    } 
};

Upvotes: 2

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