Get value using Regular Expression

標題：C/C++使用正規表示法取值
VC++ (main.cpp)：

#include "stdafx.h"
#include <iostream>
#include <regex> //string lib here

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    cout << "--- Example 1 ---" << endl;
    //String Match
    string strA = "13393774";
    smatch matchA;
    regex regA("[0-9]+");
    if(regex_match(strA, matchA, regA))
    {
        cout << atof(matchA[0].str().c_str()) << " is number." << endl;
    } else {
        cout << "Not a number." << endl;
    }

    cout << "--- Example 2 ---" << endl;
    //String Match
    string strB = "-4.472136e-001";
    smatch matchB;
    regex regB("[+-]?(?=\.[0-9]|[0-9])(?:[0-9]+)?(?:\.?[0-9]*)(?:[eE][+-]?[0-9]+)?");
    if(regex_match(strB, matchB, regB))
    {
        cout << atof(matchB[0].str().c_str()) << " is number." << endl;
    } else {
        cout << "Not a number." << endl;
    }
    
    cout << "\n--- Example 3 ---" << endl;
    //String Search
    string strC = "   facet normal 0.000000e+000 -4.472136e-001 8.944272e-001";
    smatch matchC;
    regex regC(" *facet normal \
([+-]?(?=\.[0-9]|[0-9])(?:[0-9]+)?(?:\.?[0-9]*)(?:[eE][+-]?[0-9]+)?) \
([+-]?(?=\.[0-9]|[0-9])(?:[0-9]+)?(?:\.?[0-9]*)(?:[eE][+-]?[0-9]+)?) \
([+-]?(?=\.[0-9]|[0-9])(?:[0-9]+)?(?:\.?[0-9]*)(?:[eE][+-]?[0-9]+)?)");
    if(regex_match(strC, matchC, regC))
    {
        cout << "Facet normal: (";
        cout << atof(matchC[1].str().c_str()) << ", ";
        cout << atof(matchC[2].str().c_str()) << ", ";
        cout << atof(matchC[3].str().c_str()) << ")" << endl;
    } else {
        cout << "Not Match." << endl;
    }

    return 0;
}

說明：
在C/C++中使用正規表示式取得數值。