ing类型，如下所示：std::string s = "wikipedia"; /* 正确 */s[0] = 'W';除以零会导致未定义行为。根据 IEEE 754，float、double和long double类型的值除以零的结果是无穷大或NaN：<ref name="C++03 5.6/4">ISO/IEC (2003). "ISO/IEC 14882:2003(E): Programming Languages - C++ §5.6 Multiplicative operators [exp