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 <functional>
#include <iostream>
#include <list>
#include <numeric>
#include <sstream>
#include <string>
#define int long long
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
using namespace std;

class Source {
  using iterator = std::string::iterator;
  using const_iterator = std::string::const_iterator;
  const_iterator begin, s;

public:
  Source(iterator s) : begin(s), s(s) {}
  Source(const_iterator s) : begin(s), s(s) {}

  char peek() {
    char ch = *s;
    if (!ch) throw ex("too short");
    return ch;
  }

  void next() {
    peek();
    ++s;
  }

  std::string ex(const std::string &e) {
    std::ostringstream oss;
    oss << "[pos: " << s - begin << ", char: " << *s << "] " << e << '\n';
    return oss.str();
  }

  bool operator==(const Source &t) const { return s == t.s; }
  bool operator!=(const Source &t) const { return !(*this == t); }
};

template<typename T> using Parser = std::function<T(Source &)>;

Parser<char> satisfy(const std::function<bool(char)> &f) {
  return [=](Source &s) {
    char c = s.peek();
    if (!f(c)) throw s.ex("not satisfy");
    s.next();
    return c;
  };
}

template<typename T> Parser<T> left(const std::string &e) {
  return [=](Source &s) -> T { throw s.ex(e); };
}

Parser<char> left(const std::string &e) { return left<char>(e); }

template<typename T1, typename T2> Parser<std::string> operator+(const Parser<T1> &p1, const Parser<T2> &p2) {
  return [=](Source &s) {
    std::string r;
    r += p1(s);
    r += p2(s);
    return r;
  };
}

template<typename T> Parser<std::string> operator*(int n, const Parser<T> &p) {
  return [=](Source &s) {
    std::string r;
    rep(i, n) r += p(s);
    return r;
  };
}
template<typename T> Parser<std::string> operator*(const Parser<T> &x, int n) { return n * x; }

template<typename T> Parser<std::string> many_str(const Parser<T> &p) {
  return [=](Source &s) {
    std::string r;
    try {
      for (;;) r += p(s);
    } catch (const std::string &) {}
    return r;
  };
}

Parser<std::string> many(const Parser<char> &p) { return many_str(p); }
Parser<std::string> many(const Parser<std::string> &p) { return many_str(p); }
template<typename T> Parser<std::list<T>> many(const Parser<T> &p) {
  return [=](Source &s) {
    std::list<T> v;
    try {
      for (;;) v.emplace_back(p(s));
    } catch (const std::string &) {}
    return v;
  };
}

template<typename T> Parser<std::string> many1(const Parser<T> &p) { return p + many(p); }

template<typename T> const Parser<T> operator||(const Parser<T> &p1, const Parser<T> &p2) {
  return [=](Source &s) {
    T r;
    Source back = s;
    try {
      r = p1(s);
    } catch (const std::string &) {
      if (s != back) throw;
      r = p2(s);
    }
    return r;
  };
}

template<typename T1, typename T2> Parser<T1> operator<<(const Parser<T1> &p1, const Parser<T2> &p2) {
  return [=](Source &s) {
    T1 r = p1(s);
    p2(s);
    return r;
  };
}

template<typename T1, typename T2> Parser<T2> operator>>(const Parser<T1> &p1, const Parser<T2> &p2) {
  return [=](Source &s) {
    p1(s);
    return p2(s);
  };
}

template<typename T> Parser<T> tryp(const Parser<T> &p) {
  return [=](Source &s) {
    T r;
    Source bak = s;
    try {
      r = p(s);
    } catch (const std::string &) {
      s = bak;
      throw;
    }
    return r;
  };
}

template<typename T1, typename T2> Parser<T2> fmap(const std::function<T2(const T1 &)> &f, const Parser<T1> &p) {
  return [=](Source &s) { return f(p(s)); };
}

template<typename L, typename R, typename X> Parser<std::function<X(const L &)>> fmap(const std::function<X(const L &, const R &)> &f, const Parser<R> &p) {
  return [=](Source &s) {
    R r = p(s);
    return [=](const L &l) { return f(l, r); };
  };
}

Parser<std::function<int(int)>> fmap(const std::function<int(int, int)> &f, const Parser<int> &p) { return fmap<int, int, int>(f, p); }

Parser<int> eval(const Parser<int> &p, const Parser<std::list<std::function<int(int)>>> &fs) {
  return [=](Source &s) {
    int x = p(s);
    auto xs = fs(s);
    return std::accumulate(xs.begin(), xs.end(), x, [](int a, const std::function<int(int)> &f) { return f(a); });
  };
}

auto anyChar = satisfy([](char) { return true; });

Parser<char> char1(char c) {
  return satisfy([=](char x) { return x == c; }) || left(std::string("not char '") + c + "'");
}

auto digit = satisfy([](char c) { return '0' <= c && c <= '9'; }) || left("not digit");
auto upper = satisfy([](char c) { return 'A' <= c && c <= 'Z'; }) || left("not upper");
auto lower = satisfy([](char c) { return 'a' <= c && c <= 'z'; }) || left("not lower");
auto alpha = satisfy([](char c) { return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'); }) || left("not alpha");
auto alphaNum = satisfy([](char c) { return ('0' <= c && c <= '9') || ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'); }) || left("not alphaNum");

Parser<std::string> token(const std::string &xs) {
  return [=](Source &s) {
    for (auto x : xs) (char1(x) || left("not token \"" + xs + "\""))(s);
    return xs;
  };
}

// clang-format off
extern Parser<int> factor_;
Parser<int> factor = [](Source &s) { return factor_(s); };

Parser<int> number = [](Source &s) {
  int val = 0;
  while (isdigit(s.peek())) {
    val *= 10;
    val += s.peek() - '0';
    s.next();
  }
  return val;
};

// auto number = fmap<string, int>([](const string &s) { return stoi(s); }, many1(digit));

// auto term = eval(number, many(char1('*') >> fmap([](int l, int r) { return l * r; }, factor)
//                            || char1('/') >> fmap([](int l, int r) { return l / r; }, factor)));
auto term = eval(number, many(char1('*') >> fmap([](int l, int r) { return l * r; }, number)
                           || char1('/') >> fmap([](int l, int r) { return l / r; }, number)));

auto expr = eval(term, many(char1('+') >> fmap([](int l, int r) { return l + r; }, term)
                         || char1('-') >> fmap([](int l, int r) { return l - r; }, term)));

Parser<int> factor_ = char1('(') >> expr << char1(')') || number;
// clang-format on

signed main() {
  int n;
  cin >> n;
  cin.ignore();
  while (n--) {
    string s;
    getline(cin, s);
    s.pop_back();
    Source begin = s.begin();
    // cout << expr(begin) << endl;
    try {
      cout << number(begin) << endl;
    } catch (const string &s) { cout << s << endl; }
  }
}

C++: 
#include <iostream>
#include <string>
#include <string.h>
#include <queue>
#include <vector>
#include <cctype>
using namespace std;

typedef string::const_iterator State;
int expression(State &begin);

int number(State &begin) {
	int ret = 0;
	for (; isdigit(*begin);) {
		ret *= 10;
		ret += *begin - '0';
		begin++;
	}
	return ret;
}
int factor(State &begin) {
	int ret;
	if (*begin == '(') {
		begin++;
		ret = expression(begin);
		begin++;
	}
	else {
		return number(begin);
	}
	return ret;
}
int term(State &begin) {
	int ret = factor(begin);
	for (;;) {
		if (*begin == '*') {
			ret *= term(++begin);
		}
		else if (*begin == '/') {
			ret /= term(++begin);
		}
		else break;
	}
	return ret;
}


int expression(State &begin) {
	int ret = term(begin);
	for (;;) {
		if (*begin == '+') {
			ret += term(++begin);
		}
		else if (*begin == '-') {
			ret -= term(++begin);
		}
		else break;
	}
	return ret;
}

int main() {
	int N;
	cin >> N;
	cin.ignore();
	for (int i = 0; i < N; i++) {
		string str;
		getline(cin, str);
		cout << expression(str.begin()) << endl;
	}
	return 0;
}