A command-line calculator using infix to postfix in C++

I was in the mood for some C++ and decided to write a command line calculator, which understands addition, subtraction, multiplication and parentheses. See what I have:

main.cpp

```
#include
#include
#include
#include
#include
#include
#include
#include
#include

using std::cin;
using std::copy;
using std::cout;
using std::endl;
using std::isspace;
using std::ostream_iterator;
using std::pair;
using std::runtime_error;
using std::stack;
using std::string;
using std::stringstream;
using std::vector;

enum class TokenType {
OPERAND,
OPERATOR
};

enum class Operator {
PLUS,
MINUS,
MULTIPLY,
LEFT_PARENTHESIS,
RIGHT_PARENTHESIS
};

static int get_operator_precedence(Operator _operator)
{
switch (_operator) {
case Operator::PLUS:
case Operator::MINUS:
return 1;

case Operator::MULTIPLY:
return 0;

default:

if (_operator == Operator::LEFT_PARENTHESIS)
{
throw runtime_error(
"Left parenthesis has no precedence assigned to it.");
}

if (_operator == Operator::RIGHT_PARENTHESIS)
{
throw runtime_error(
"Right parenthesis has no precedence assigned to it.");
}

throw std::runtime_error(
"Unknown operator. This should not happen.");
}
}

class Token
{
TokenType m_token_type;
Operator m_operator;
int m_operand;

public:
Token(int operand) : m_operand{operand},
m_token_type{TokenType::OPERAND} {}

Token(Operator _operator) : m_operand{0},
m_token_type(TokenType::OPERATOR),
m_operator{_operator} {}

TokenType get_token_type() const
{
return m_token_type;
}

Operator get_operator() const
{
return m_operator;
}

int get_operand() const
{
re

Quite nice. A couple of small things:

• you can use emplace_back instead of push_back when adding Tokens. Likewise for the stack with emplace instead of push

• for the sake of symetry, do out






• check your IO: your mainloop should be while (getline(cin, expr)) { ... } to detect EOF






• don't use _variable` for names.

StackExchange Code Review Q#135672, answer score: 4