Go: package main

import (
	"bufio"
	"fmt"
	"go/token"
	"go/types"
	"os"
	"strconv"
	"strings"
)

func main() {
	stdin := bufio.NewScanner(os.Stdin)
	stdin.Scan()
	n, _ := strconv.Atoi(stdin.Text())
	for i := 0; i < n; i++ {
		stdin.Scan()
		exp := strings.TrimRight(stdin.Text(), "=")
		res, _ := types.Eval(token.NewFileSet(), nil, token.NoPos, exp)
		fmt.Println(res.Value)
	}
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <stack>
#include <vector>
#include <stdio.h>

using namespace std;

int getPriority(char ch){
  switch(ch){
  case '+':
    return 0;
  case '-':
    return 1;
  case '/':
    return 2;
  case '*':
    return 3;
  default:
    return -1;
  }
}

vector<string> toReversePorland(string str){

  vector<string> hand;
  vector<string> side;
  
  for(int i = 0; i < str.size(); i++){
    if(str[i] == ' ')
      continue;
    else if(str[i] == '=')
      break;
    if(str[i] >= '0' && str[i] <= '9'){
      string num;
      while(i < str.size()){
	if(str[i] < '0' || str[i] > '9'){
	  break;
	}
	num += str[i];
	i++;
      }
      hand.push_back(num);
      i--;
    }
    else if(str[i] == '('){
      string tmp;
      tmp += str[i];
      side.push_back(tmp);
    }
    else if(str[i] == ')'){
      // ツ右ツ環古環づ慊づ可可算ツ子ツづーツ暗ェツづつつクツづつ偲ィツ個ウツづ可姪淞つキ
      for(int j = side.size()-1 ; ;j--){
	if(side[j] == "("){
	  if(j != 0){
	    vector<string> tmp;
	    for(int k = 0; k < j; k++){
	      tmp.push_back(side[k]);
	    }
	    side = tmp;
	  }
	  else
	    side.clear();
	  break;
	}
	else{
	  string tmp = side[j];
	  hand.push_back(tmp);
	}
      }
    }
    else{
      if(side.size() == 0){
	string tmp;
	tmp += str[i];
	side.push_back(tmp);
      }
      else{
	char cs = side[side.size()-1][0];
	if((cs == '*' || cs == '/') && (str[i] == '*' || str[i] == '/')){
	  hand.push_back(side[side.size()-1]);
	  string tmp;
	  tmp += str[i];
	  side[side.size()-1] = tmp;
	}
	else if(cs != '+' && cs != '-' && cs != '*' && cs != '/'){
	  string tmp;
	  tmp += str[i];
	  side.push_back(tmp);
	}
	else{
	  if(getPriority(str[i]) < getPriority(cs)){
	    hand.push_back(side[side.size()-1]);
	    string tmp;
	    tmp += str[i];
	    side[side.size()-1] = tmp;
	  }
	  else{
	    string tmp;
	    tmp += str[i];
	    side.push_back(tmp);
	  }
	}
      }
    }
  }

  for(int i = side.size()-1; i >= 0; i--){
    string tmp;
    hand.push_back(side[i]);
  }
  return hand;
}


long long calc(vector<string> str){
  stack<long long> st;
  for(int i = 0; i < str.size(); i++){
    if(str[i] == "+" || str[i] == "-" || str[i] == "*" || str[i] == "/"){
      long long val[2];
      val[0] = st.top();
      st.pop();
      val[1] = st.top();
      st.pop();
      if(str[i] == "+"){
	st.push(val[0] + val[1]);
      }
      if(str[i] == "-"){
	st.push(val[1] - val[0]);
      }
      if(str[i] == "*"){
	st.push(val[0] * val[1]);
      }
      if(str[i] == "/"){
	st.push(val[1] / val[0]);
      }
    }
    else{
      st.push(atoi(str[i].c_str()));
    }
  }
  return st.top();
}

int main(){

  int n;
  string s;
  cin >> n;
  
  vector<string> input;
  string str;
  for(int i = 0; i < n; i++){
    cin >> str;
    input.push_back(str);
  }

  for(int i = 0; i < n; i++){
    str = input[i];
    // vector<string> vec = toReversePorland(str);
    // for(int i = 0; i < vec.size(); i++)
    //   cout << vec[i] << endl;
    cout << calc(toReversePorland(str)) << endl;
  }
  
  return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>

using namespace std;

int compute(string s) {
    int begin;
    int nest = 0;
    int n = 0;
    vector<int> children, children2;
    vector<char> operators, operators2;

    for (int i=0; i<(int)s.length(); i++) {
        if (s[i] == '(') {
            nest++;
            if (nest == 1) {
                begin = i+1;
            }
        }
        else if (s[i] == ')') {
            if (nest == 1) {
                string substr = s.substr(begin, i-begin);
                n = compute(substr);
            }
            nest--;
        }
        else if (nest == 0) {
            if ('0' <= s[i] && s[i] <= '9') {
                n *= 10;
                n += s[i]-'0';
            }
            else {
                children.push_back(n);
                operators.push_back(s[i]);
                n = 0;
            }
        }
    }
    children.push_back(n);
    children2.push_back(children[0]);
    for (int i=0; i<(int)operators.size(); i++) {
        if (operators[i] == '*') {
            children2[children2.size()-1] *= children[i+1];
        }
        else if (operators[i] == '/') {
            children2[children2.size()-1] /= children[i+1];
        }
        else {
            children2.push_back(children[i+1]);
            operators2.push_back(operators[i]);
        }
    }
    n = children2[0];
    for (int i=0; i<(int)operators2.size(); i++) {
        if (operators2[i] == '+') {
            n += children2[i+1];
        }
        else {
            n -= children2[i+1];
        }
    }
    return n;
}

int main() {
    int n;
    string s;
    cin >> n;
    for (int i=0; i<n; i++) {
        cin >> s;
        cout << compute(s.substr(0, s.length()-1)) << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <string>
#include <cctype>
#include <vector>
#include <stdexcept>
using namespace std;
string input;

inline bool is_all_digit(string &in)
{
	for (auto i : in)
	{
		if (!isdigit(i))
			return false;
	}
	return true;
}
vector<string> split(string in)
{
	vector<string> spl;
	int pos = 0;
	if (in[pos] == '-') 
	{
		pos++;
		while (pos < in.size()) {
			if (isdigit(in[pos])) {
				pos++;
			}
			else {
				break;
			}
		}
		spl.push_back(in.substr(0, pos));
		in.erase(0, pos);
		pos = 0;
	}
	while ( pos < in.size())
	{
		if (!isdigit(in[pos]))
		{
			if (pos != 0)
			{
				spl.push_back(in.substr(0, pos));
				in.erase(0, pos);
				pos = 0;
			}
			else
			{
				if (in[0] == '(')
				{
					int cnt = 1;
					int r_pos = 1;
					for (r_pos = 1; r_pos < in.size(); r_pos++)
					{
						if (in[r_pos] == '(')
							cnt++;
						if (in[r_pos] == ')')
							cnt--;
						if (cnt == 0)
							break;
					}
					spl.push_back(in.substr(pos + 1, r_pos - 0 - 1));
					in.erase(0, r_pos + 1);
					pos = 0;
					continue;
				}
				else if (in[0] == '+' || in[0] == '-' || in[0] == '*' || in[0] == '/')
				{
					spl.push_back(in.substr(0, 1));
					in.erase(0, 1);
					pos = 0;
				}
			}
		}
		else {
			pos++;
		}
	}
	if (in.size() != 0) spl.push_back(in);
	return spl;
}
int cal(string &in_str) {
	auto in = split(in_str);
	while (in.size() == 1 && !is_all_digit(in[0])) {
		in = split(in[0]);
	}
	while (in.size() != 1) {
		auto pos = in.begin();
		while (pos != in.end()) 
		{
			if (*pos == "*") {
				pos--;
				*pos = to_string(cal(*pos)*cal(*(pos + 2)));
				in.erase(pos+1 , pos + 3);
			}
			else if (*pos == "/") {
				pos--;
				*pos = to_string(cal(*pos)/cal(*(pos + 2)));
				in.erase(pos+1, pos + 3);
			}
			if (in.size()==1) break;
			if (pos != in.end()) pos++;
		}
		pos = in.begin();
		while (pos != in.end()) {
			if (*pos == "+") {
				pos--;
				*pos = to_string(cal(*pos)+cal(*(pos + 2)));
				in.erase(pos+1, pos + 3);
			}
			else if (*pos == "-") {
				pos--;
				*pos = to_string(cal(*pos) - cal(*(pos + 2)));
				in.erase(pos+1, pos + 3);
			}
			if (in.size()==1) break;
			if(pos != in.end()) pos++;
		}
	}
	try {
		return(stoi(in[0]));
	}
	catch (const std::invalid_argument& a) {
		cerr << a.what() << input << endl;
	}
}
int main()
{
	
	int n;
	cin >> n;
	cerr<<n<<endl;
	while (n--) {
		cin >> input;
		//input.erase(input.end() - 1);
		//cout << cal(input) << endl;
		cerr << input << endl;
	}

	return 0;
}