+-*/

template<class T> T string_cast(const std::string& v){std::stringstream ss;ss << v;T ret;ss >> ret;return ret;}template<class T> std::string to_string( T v){std::stringstream ss;ss << v;return ss.str();}std::string op_v(const char c){std::string ret;ret += c;return ret;}typedef std::string (*op_function)(const std::string&l,const std::string& r);std::string add(const std::string& l,const std::string& r){double v = string_cast<double>(l);return to_string(v + string_cast<double>(r));}std::string sub(const std::string& l,const std::string& r){return to_string(string_cast<double>(l) - string_cast<double>(r));}std::string mut(const std::string& l,const std::string& r){return to_string(string_cast<double>(l) * string_cast<double>(r));}std::string div(const std::string& l,const std::string& r){return to_string(string_cast<double>(l) / string_cast<double>(r));}std::string assign(const std::string& l,const std::string& r){return l + "=" + r;}struct double_calc{std::string op;double_calc *left,*right,*parent;public:double_calc():  op(""),left(NULL),right(NULL),parent(this){  }  double_calc(const std::string& v):  op(v),left(NULL),right(NULL),parent(NULL){  }public:double_calc* insert_left_node(const std::string& v){left = new double_calc(v);left->parent = this;return left;}double_calc* insert_rigt_node(const std::string& p,const std::string& v) {right = new double_calc(p);right->insert_left_node(v);right->parent = this;return right;}double_calc* insert_low_node(const std::string& p,const std::string& v){double_calc* node = new double_calc(p);parent->right = node;node->left = this;right = new double_calc(v);parent = node;return right;}public:void midle_show(){if(NULL != left){left->midle_show();}std::cout << op ;if(NULL != right){right->midle_show();}}};class alg_calculater {public:alg_calculater():calc_tree(){current_item = &calc_tree;op_mapping["+"] = add;op_mapping["-"] = sub;op_mapping["*"] = mut;op_mapping["/"] = div;op_mapping["="] = assign;}public:std::string do_script(const std::string& script){std::for_each(script.begin(),script.end(),boost::bind(&alg_calculater::create_inner_tree,this,boost::lambda::_1));calc_tree.midle_show();std::cout << std::endl;return op_tree(&calc_tree);}protected:std::string op_tree(const double_calc*const node){if(NULL == node->left && NULL == node->right){return node->op;}op_function fun =  op_mapping[node->op];std::string l = op_tree(node->left);std::string r = op_tree(node->right);return fun(l,r);}protected:double_calc calc_tree;double_calc* current_item;void create_inner_tree(const char c) {switch (c) {case ' ': {break;  }case ';':{current_item->right = new double_calc(value);current_item->right->parent = current_item;value.clear();break; }case '=':{current_item->op = op_v(c);current_item = current_item->insert_left_node(value);current_item = current_item->parent;value.clear();break;}case '+':case '-':{if(current_item->op == "*" || current_item->op == "/"){current_item->right = new double_calc(value);for(current_item = current_item->parent;current_item;current_item = current_item->parent){if(current_item->op == "+" || current_item->op == "-" || current_item->op == "="){break;}}double_calc* node = new double_calc(op_v(c));node->left = current_item->right;node->parent = current_item;current_item->right = node;current_item = node;}else{current_item = current_item->insert_rigt_node(op_v(c),value);}value.clear();break; }case '/':case '*':{current_item = current_item->insert_rigt_node(op_v(c),value);value.clear();break; }default: {value += c;break; }}}protected:std::string value;std::map<std::string,op_function> op_mapping;};