表达式求值的程序

 没事干自己写了个表达式求值的程序，欢迎个位指正。

#include <cassert>#include <iostream>#include <stack>using namespace std;const char operators[]={')','+','-','*','/','('};void calculate(stack<char>& stack_operator,stack<double>& stack_number){int second = stack_number.top();stack_number.pop();int first = stack_number.top();stack_number.pop();char calc_operator = stack_operator.top();stack_operator.pop();double calc_result = 0;switch(calc_operator){case '+':calc_result = first + second;break;case '-':calc_result = first - second;break;case '*':calc_result = first * second;break;case '/':calc_result = first / second;break;default:assert(false);break;}stack_number.push(calc_result);}//该方法只支持整形计算，并且不考虑错误情况double calculate(char* expression){stack<char> stack_operator;stack<double> stack_number;while(*expression != '/0'){//operatorif(*expression<'0' || *expression>'9'){if(stack_operator.empty()){stack_operator.push(*expression);}else{char top_operator = stack_operator.top();bool is_precede = false;for(int i=0;i<sizeof(operators)/sizeof(*operators);i++){if(operators[i] == top_operator){is_precede = true;break;}if(operators[i] == *expression){is_precede = false;break;}}if(is_precede || top_operator == '('){stack_operator.push(*expression);}else{calculate(stack_operator,stack_number);if(*expression == ')'){stack_operator.pop();}else{stack_operator.push(*expression);}}}}//numberelse{int num=0;while(*expression>='0' && *expression <='9'){num = num*10+*expression-'0';expression++;}stack_number.push(num);continue;}expression++;}while(!stack_operator.empty()){calculate(stack_operator,stack_number);}return stack_number.top();}int main(){cout<<calculate("2*(3-2)*(50-30)")<<endl; return 0;}