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 = ;
     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 +  && for_text[pos + ] == 'm') || (for_text.size() >= pos +  && for_text[pos + ] == 'm' && for_text[pos + ] >= '' && for_text[pos + ] <= ''))
         {
             for_text.replace(pos, searchStr.size(), replaceStr);
         }
         pos++;
     }

     vector<string> lVector;
     vector<string> rVector;
     int lastSplitIdx = ;
     string lastText("");
     for (string::size_type i = ; 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() > )
                 {
                     lVector.push_back(lastText);
                     rVector.push_back(for_text.substr(lastSplitIdx, i - lastSplitIdx));
                 }
                 lastText = "";
             }
             lastSplitIdx = i + ;
         }
     }
     if (lastSplitIdx != for_text.size())
     {
         if (lastText.size() > )
         {
             lVector.push_back(lastText);
             rVector.push_back(for_text.substr(lastSplitIdx, lastText.size() - lastSplitIdx));
         }
     }

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

     pos = ;
     int parseIdx = ;
     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(, );
         string ower = leftStr;
         if (category == "" || category == "" || category == "" || category == "" || category == "")
         {
             rightStr = rightStr.substr(, rightStr.size());
         }
         else
         {
             category = "";
         }
         if (leftStr.find("self", ) != string::npos)
         {
             ower = "src";
         }
         else if (leftStr.find("target", ) != 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 ;
 }    

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[].first, mat[].second);
         string category(mat[].first, mat[].second);
         string attrName(mat[].first, mat[].second);
         if (category.compare("") == )
         {
             category = "";
         }
         if (object.find("self", ) != string::npos)
         {
             object = "src";
         }
         else if (object.find("target", ) != string::npos)
         {
             object = "dst";
         }
         string replaceStr(object + ":lf_" + attrName + "(" + category + ")");
         for_text.replace(mat[].first, mat[].second, replaceStr);
         startPos = for_text.begin();
         endPos = for_text.end();
     }
 }