string::size_type 用的不错

#include "stdafx.h"#include <iostream>#include <string>#include <sstream>using namespace std;bool isZero(string testNum, string::size_type index){string testZero('0', index);if (!testNum.compare(index, (testNum.size() - index), testZero)){return true;}else{return false;}}bool isDecimal(string inputNum){string::size_type decimalPointIndex = inputNum.find(".");if (decimalPointIndex <= inputNum.size()&& !isZero(inputNum, decimalPointIndex)){return true;}else{return false;}}int main(void){double inputNumber;cin >> inputNumber;stringstream  ss;string strNum;ss << inputNumber;ss >> strNum;bool flg = isDecimal(strNum);if (flg){cout << "这是小数" << endl;}else{cout << "这不是小数" << endl;}return 0;}