作者在 2010-07-02 19:56:08 发布以下内容
#include <string>
template <typename T>
inline T const& max(T a,T b)
{
return a<b?b:a;
}
int main()
{
std::string s;
const char *a1="apple",*a2="peach";
const char aa1[]="apple",aa2[]="peacha";
::max(a1,a2);
::max(aa1,aa2);
::max("apple","peach");
::max("apple","peacha");
return 0;
}
此时模板把 peacha 之类的认为是字符串，因此只是一个指针template <typename T>
inline T const& max(T a,T b)
{
return a<b?b:a;
}
int main()
{
std::string s;
const char *a1="apple",*a2="peach";
const char aa1[]="apple",aa2[]="peacha";
::max(a1,a2);
::max(aa1,aa2);
::max("apple","peach");
::max("apple","peacha");
return 0;
}
#include <string>
template <typename T>
inline T const& max(T const& a,T const& b)
{
return a<b?b:a;
}
int main()
{
std::string s;
const char *a1="apple",*a2="peach";
const char aa1[]="apple",aa2[]="peacha";
::max(a1,a2);
::max(aa1,aa2); // error
::max("apple","peach");
::max("apple","peacha"); // error
return 0;
}
此时两处error均是因为template <typename T>
inline T const& max(T const& a,T const& b)
{
return a<b?b:a;
}
int main()
{
std::string s;
const char *a1="apple",*a2="peach";
const char aa1[]="apple",aa2[]="peacha";
::max(a1,a2);
::max(aa1,aa2); // error
::max("apple","peach");
::max("apple","peacha"); // error
return 0;
}
error C2782: 'const T &__cdecl max(const T &,const T &)' : template parameter 'T' is ambiguous
could be 'const char [7]' or 'const char [6]'
也就是此时被认为是数组（地址确定的指针），因此认为长度不一致的数组认为不同的类型
