invalid conversion from ‘const int*’ to ‘int*’ in template function

Question

class A{
 private:
 T x;
 public:
 A():x(0){}
 A(T x1):x(x1){}
 void printInfo(const T& a){
 cout<<"Succes1"<<endl;
 }
};
class B{
 private:
 int x;
 A<int*> var;
 public:
 B():x(0){}
 B(int x1):x(x1){}
 void printInfo(const int * a){
 var.printInfo(a);
 }
};

The probelms is with

void printInfo(const int * a){
 var.printInfo(a);
}

It gives an error, saying invalid conversion from ‘const int*’ to ‘int*’

but works with int *a or int *const a

Shouldn't void printInfo in class A look like

void printInfo(const int* a)

Is this correct?

cont int *p, //pointer to constant int
int* const p //constant pointer to int

if thats the case there should be error with

printInfo(int* const a)

not with

printInfo(const int * a)

Answer 1

Shouldn't void printInfo in class A look like

void printInfo(const int* a)

Is this correct?

No, the problem ist that you declare var as A<int*> in B, so A's

void printInfo(const T& a); 

is really

void printInfo( int* const& a); 

and not

void printInfo( int const* & a); 

So, for the call in B to work you need to declare var as A<int const*>. See compiling version here.

Answer 2

void printInfo(const int * a){

Shouldn't void printInfo in class B look like

void printInfo(const int* a)

Is this correct?

Both are equivalent. In many cases, whitespace is not syntactically relevant.

cont int *p, //pointer to constant int
int* const p //constant pointer to int

These are correct.

if thats the case there should be error with

printInfo(int* const a)

not with

printInfo(const int * a)

The error should be when you attempt to implicitly convert a pointer to const into pointer to non-const.

• R4de: I've meant to say Shouldn't void printInfo in class A look like void printInfo(const int* a). Then why does it trying to convert pointer to const into pointer to non const when functions parameters in both classes are the same