arguments a constant in template function

Question

I have a template function as below which has one of the arguments a constant

template<typename T>
T maxAmong( T x, const T y) {
    return x ;
}

For explicit specialization I expected to have the below code. But this gives a compile error.

template<>   char* maxAmong(  char* x, const char* y) {
    return x;
}

Whereas the making both return type and both arguments const works

template<>  const char* maxAmong( const char* x, const char* y) {
    return x;
}

Why does the code in second snippet fail as for me the code looks more right that way.

`template<> char* maxAmong( char* x, char* const y) {` this is constant pointer. You have pointer to constant, this is a difference. — rafix07, Oct 07 '21 at 06:58
In the specialisation I was expecting the type T to be char*. So 1st argument and return type to be char* and second argument a const char*( const of type T as in the original template definition). — ArunJose, Oct 07 '21 at 07:01
The second argument is actually a `char* const` not `const char*`. — 康桓瑋, Oct 07 '21 at 07:03

score 4 · Accepted Answer · answered Oct 07 '21 at 07:07

const char * is a pointer to a const char.

char * const is a constant pointer to a char.

Thus, your template specialization should look like this:

template<typename T>
T maxAmong( T x, const T y) {
    return x ;
}

template<> 
char* maxAmong( char* x,  char* const y) {
    return x;
}

This thread might be helpful as well.

1 Answers1