C++ Templates笔记 3 重载函数模板(附加)

#include <iostream>#include <cstring>#include <string>// maximum of two values of any typetemplate <typename T>inline T const& max (T const& a, T const& b){return a < b ? b : a;}// maximum of two pointerstemplate <typename T>inline T* const& max (T* const& a, T* const& b){return *a < *b ? b : a;}// maximum of two C-stringsinline char const* const& max (char const* const& a, char const* const& b){ return std::strcmp(a,b) < 0 ? b : a;}int main (){int a=7;int b=42;::max(a,b); // max() for two values of type intstd::string s="hey";std::string t="you";::max(s,t); // max() for two values of type std::stringint* p1 = &b;int* p2 = &a;::max(p1,p2); // max() for two pointerschar const* s1 = "David";char const* s2 = "Nico";::max(s1,s2); // max() for two C-strings}/*在上面的所有重载的实现里面，我们都是通过引用来传递每个实参的。在重载函数模板的时候，最好只改变那些需要改变的内容！所以有颇费周折的inline char const* const& max (char const* const& a,char const* const& b)*/#include <iostream>#include <cstring>#include <string>// maximum of two values of any type (call-by-reference)template <typename T>inline T const& max (T const& a, T const& b){ return a < b ? b : a;}// maximum of two C-strings (call-by-value)inline char const* max (char const* a, char const* b){ return std::strcmp(a,b) < 0 ? b : a;}// maximum of three values of any type (call-by-reference)template <typename T>inline T const& max (T const& a, T const& b, T const& c){ return max (max(a,b), c); // error, if max(a,b) uses call-by-value}int main (){ ::max(7, 42, 68); // OK const char* s1 = "frederic"; const char* s2 = "anica"; const char* s3 = "lucas"; ::max(s1, s2, s3); // ERROR}/*注意调用return max (max(a,b),c);是错误的！对于C-string而言，这里max(a,b)产生了一个新的临时局部值，该值可能被外面的max函数以引用的方式返回，这个将导致传回无效的引用！！这个错误的可能性仅仅是可能，不是必然！inline T const& max (T const& a, T const& b, T const& c)传回的是引用！*/template <typename T>inline T const& max (T const& a, T const& b){ return a < b ? b : a;}// maximum of three values of any typetemplate <typename T>inline T const& max (T const& a, T const& b, T const& c){ return max (max(a,b), c); // uses the template version even for ints} // because the following declaration comes // too late:// maximum of two int valuesinline int const& max (int const& a, int const& b) { return a < b ? b : a;}/*函数的所有重载版本的声明都应该位于该函数被调用的位置之前*/