Templates and explicit specializations

I have a template

template<class T>
T maxn(T *, int);


and explicit specialization for char*

char*

template<> char* maxn(char**, int);


And I want to add const,

const

T maxn(const T *, int);


but after adding const in explicit specialization there is an error.

template<>char* maxn<char*>(const char**, int);


Why? Who can explain to me?

P.S. Sorry for my English.))

const

2 Answers
2

Given the parameter type const T *, const is qualified on T. Then for char* (the pointer to char) it should be char* const (const pointer to char), but not const char* (non-const pointer to const char).

const T *

const

T

char*

char

char* const

const

char

const char*

const

char

template<class T>
T maxn(const T *, int);

template<>
char* maxn<char*>(char* const *, int);
// ~~~~~


maxn(T *, int);

maxn(const T *, int);

const

You should instantiate the method for const char*:

const char*

template<> const char* maxn<const char*>(const char**, int);


template<>char* maxn<char*>(const char**, int); doesn't correspond to

template<>char* maxn<char*>(const char**, int);

template<class T>
T maxn(T *, int);


signature, so you can't just add const to one parameter.

const

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