6.5.2 内联函数和constexpr函数

书中页数：P213
代码名称：inline_shorter.cc

#include <string>
using std::string;

#include <iostream>
using std::cout; using std::endl;

//inline version: find the shorter of two strings
inline const string &
shorterString(const string &s1, const string &s2)
{
        return s1.size() <= s2.size() ? s1 : s2;
}

int main()
{
	string s1("successes"), s2("failure");
	cout << shorterString(s1, s2) << endl;

	// call the size member of the string returned by shorterString
	cout << shorterString(s1, s2).size() << endl;

	// equivalent code as generated by the call to inline version
	// of shorterString
	cout << (s1.size() < s2.size() ? s1 : s2) << endl;
	return 0;
}