cs303project2/Operator.cpp at master · aledgin/cs303project2 · GitHub

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// Alfred Ledgin, Luke Simmons, and Megan Sword
// 11/4/2015
// CS 303
// Project 2

#include <iostream>
#include <string>
#include "Operator.h"
using namespace std;


Operator::Operator()
{
    type = "(";
    precedence = 0;
    category = 'p';
}


Operator::Operator(string input)
{
    type = input;
    fixType();
    setPrecedence();
    setCategory();
}


const double Operator::execute(double rhs) const
{

    if (category == 'u')
    {

        // The type is hard-coded upon operator construction.
        if (type == "!")
        {
            if (rhs == 0)
                return 1;
            else
                return 0;
        }
        else if (type == "++")
            return rhs + 1.0;
        else if (type == "--")
            return rhs - 1.0;
        else // if (type == "-#")
            return -rhs;

    }

    else // Cannot use this function with binary operator or parentheses.
        throw
            std::exception("lhs operand required. Cannot execute parentheses");

}


const double Operator::execute(double lhs, double rhs) const
{

    if (category == 'b')
    {

        // The type is hard-coded upon operator construction.
        if (type == "^")
            return pow(lhs, rhs);
        else if (type == "*")
            return lhs * rhs;
        else if (type == "/")
        {
            if (rhs != 0)
                return lhs / rhs;
            else
                throw std::exception("Cannot divide by zero.");
        }
        else if (type == "%")
            return int(lhs) % int(rhs);
        else if (type == "+")
            return lhs + rhs;
        else if (type == "-")
            return lhs - rhs;
        else if (type == "<")
            return lhs < rhs;
        else if (type == "<=")
            return lhs <= rhs;
        else if (type == ">=")
            return lhs >= rhs;
        else if (type == ">")
            return lhs > rhs;
        else if (type == "==")
            return lhs == rhs;
        else if (type == "!=")
            return lhs != rhs;
        else if (type == "&&")
            return lhs && rhs;
        else // if (type == "||")
            return lhs || rhs;

    }

    else // Cannot use this function with unary operator or parentheses.
        throw std::exception("Cannot have lhs operand.");

}


void Operator::setPrecedence()
{
    if ((type == "(") || (type == ")"))
        precedence = 0; // Special precedence for parentheses.
    else if ((type == "!") || (type == "++")
        || (type == "--") || (type == "-#"))
        precedence = 8;
    else if (type == "^")
        precedence = 7;
    else if ((type == "*") || (type == "/") || (type == "%"))
        precedence = 6;
    else if ((type == "+") || (type == "-"))
        precedence = 5;
    else if ((type == "<") || (type == "<=")
        || (type == ">=") || (type == ">"))
        precedence = 4;
    else if ((type == "==") || (type == "!="))
        precedence = 3;
    else if (type == "&&")
        precedence = 2;
    else if (type == "||")
        precedence = 1;
    else
        throw std::exception("Invalid operator input");
}


void Operator::setCategory()
{
    if (precedence == 0)
        category = 'p'; // Parentheses have precedence == 0.
    else if (precedence == 8)
        category = 'u'; // Unary operators have precedence == 8.
    else
        category = 'b'; // Binary operators have precedence in [1, 7].
}


void Operator::fixType()
{
    if (type.length() > 1)
    {
        if (type[1] == ' ')
        {
            type = type.substr(0, 1);
            // Reference (for using substr function):
                // "std::string::substr." _cplusplus.com_. cplusplus.com, 2015.
                    // Web. 4 Nov. 2015.
                    // <http://www.cplusplus.com/reference/string/string/substr/>.
        }
    }
}