C++正则表达式例子

给了策划配置公式的地方，需要将策划配置的公式文本转化为可执行的脚本代码：
比如：self->mHp*2+target->2mMp*GetHit()+ self_mon->4mDan/1000 ==> self:lf_mHp(0)*2+dst:lf_mMp(2)*GetHit()+ src:lf_mDan(4)/1000

意思就是
1 指针变量凡是含有self的都变为src,target的都替换为dst
2 调用的属性前面的系数要提取出来
3 属性可能是多种多样的，所以提取方法不能写死。

当时时间紧急，对正则表达式也不熟，按照字符串分割的方法实现了。

代码如下：

void TestFormula(std::string& for_text)
{
    using std::string;
    using std::vector;
    string::size_type pos = 0;
    string searchStr = "->";
    string replaceStr = "#";

    if (for_text.find(searchStr) == string::npos)
    {
        return;
    }

    while ( (pos = for_text.find(searchStr, pos)) != string::npos)
    {
        if ((for_text.size() >= pos + 2 && for_text[pos + 2] == 'm') || (for_text.size() >= pos + 3 && for_text[pos + 3] == 'm' && for_text[pos + 2] >= '0' && for_text[pos + 2] <= '9'))
        {
            for_text.replace(pos, searchStr.size(), replaceStr);
        }
        pos++;
    }
        
    vector<string> lVector;
    vector<string> rVector;
    int lastSplitIdx = 0;
    string lastText("");
    for (string::size_type i = 0; i < for_text.size(); i++)
    {
        if (for_text[i] == '+' || for_text[i] == '-' || for_text[i] == '*' || for_text[i] == '/'
            || for_text[i] == '#' || for_text[i] == '(' || for_text[i] == ')' || for_text[i] == ',')
        {
            if (for_text[i] == '#')
            {
                lastText = for_text.substr(lastSplitIdx, i - lastSplitIdx);
            }
            else 
            {
                if (lastText.size() > 0)
                {
                    lVector.push_back(lastText);
                    rVector.push_back(for_text.substr(lastSplitIdx, i - lastSplitIdx));
                }
                lastText = "";
            }
            lastSplitIdx = i + 1;
        }
    }
    if (lastSplitIdx != for_text.size())
    {
        if (lastText.size() > 0)
        {
            lVector.push_back(lastText);
            rVector.push_back(for_text.substr(lastSplitIdx, lastText.size() - lastSplitIdx));
        }
    }

    if (lVector.size() == 0 || rVector.size() == 0 || lVector.size() != rVector.size())
    {
        return;
    }

    pos = 0;
    int parseIdx = 0;
    while ( ( pos = for_text.find(replaceStr, pos)) != string::npos)
    {
        string leftStr = lVector.at(parseIdx);
        string rightStr = rVector.at(parseIdx);
        string oldStr = leftStr + replaceStr + rightStr;
        string category = rightStr.substr(0, 1);
        string ower = leftStr;
        if (category == "0" || category == "1" || category == "2" || category == "3" || category == "4")
        {
            rightStr = rightStr.substr(1, rightStr.size());
        }
        else
        {
            category = "0";
        }
        if (leftStr.find("self", 0) != string::npos)
        {
            ower = "src";
        }
        else if (leftStr.find("target", 0) != string::npos)
        {
            ower = "dst";
        }
        string newStr = ower + ":lf_" + rightStr + "(" + category + ")";
        for_text.replace(pos - leftStr.size(), oldStr.size(), newStr);
        parseIdx++;
        pos++;
    }
}
int main()
{
    std::string text("self->mHp*2+target->2mMp*GetHit()+self_mon->4mDan/1000");
    std::cout << text.c_str() << std::endl;
    TestFormula(text);
    std::cout<<text.c_str()<<std::endl;

    return 0;
}    

运行结果：

颇费周折有木有~~~，还有很多临界状态需要检查，一不留神可能就踩到坑里了。

索性，看了看正则表达式，发现非常好用。代码少很多，结果一模一样。

void TestFormulaRegex(std::string& for_text)
{
    using std::string;
    std::regex pat("([A-Za-z_]+)->([0-4]*)(m[A-Za-z]+)");
    string::const_iterator startPos = for_text.begin();
    string::const_iterator endPos = for_text.end();
    std::smatch mat;
    while (std::regex_search(startPos, endPos, mat, pat))
    {
        string object(mat[1].first, mat[1].second);
        string category(mat[2].first, mat[2].second);
        string attrName(mat[3].first, mat[3].second);
        if (category.compare("") == 0)
        {
            category = "0";
        }
        if (object.find("self", 0) != string::npos)
        {
            object = "src";
        }
        else if (object.find("target", 0) != string::npos)
        {
            object = "dst";
        }
        string replaceStr(object + ":lf_" + attrName + "(" + category + ")");
        for_text.replace(mat[0].first, mat[0].second, replaceStr);
        startPos = for_text.begin();
        endPos = for_text.end();
    }
}