calculator-gui-cpp/calc.cpp at main · MahaveerPandey8290/calculator-gui-cpp · GitHub

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#include <iostream>
#include <string>
#include <stack>
#include <cmath>
#include <fstream>
#include <cctype>
using namespace std;

class Calculator {
private:
    double performOperation(double a, double b, char op) {
        switch (op) {
            case '+': return a + b;
            case '-': return a - b;
            case '*': return a * b;
            case '/':
                if (b == 0) {
                    cerr << "Error: Division by zero!" << endl;
                    return NAN;
                }
                return a / b;
            default: return 0;
        }
    }

    int precedence(char op) {
        if (op == '+' || op == '-') return 1;
        if (op == '*' || op == '/') return 2;
        return 0;
    }

    void applyOperation(stack<double>& values, stack<char>& operators) {
        if (values.size() < 2 || operators.empty()) return;
        double b = values.top(); values.pop();
        double a = values.top(); values.pop();
        char op = operators.top(); operators.pop();
        values.push(performOperation(a, b, op));
    }

    double processExpression(const string& expression) {
        stack<double> values;
        stack<char> operators;
        int i = 0;

        while (i < expression.length()) {
            if (isspace(expression[i])) {
                i++;
                continue;
            }

            if (expression[i] == '(') {
                operators.push(expression[i]);
                i++;
            }
            else if (expression[i] == ')') {
                while (!operators.empty() && operators.top() != '(') {
                    applyOperation(values, operators);
                }
                if (!operators.empty() && operators.top() == '(')
                    operators.pop();
                i++;
            }
            else if (isdigit(expression[i]) || expression[i] == '.' ||
                    (expression[i] == '-' &&
                    (i == 0 || (!isdigit(expression[i - 1]) && expression[i - 1] != ')')))) {
                // Handle negative number
                string numStr = "";
                if (expression[i] == '-') numStr += expression[i++];
                while (i < expression.length() && (isdigit(expression[i]) || expression[i] == '.')) {
                    numStr += expression[i++];
                }
                values.push(stod(numStr));
            }
            else if (expression[i] == '+' || expression[i] == '-' ||
                     expression[i] == '*' || expression[i] == '/') {
                while (!operators.empty() && precedence(operators.top()) >= precedence(expression[i])) {
                    applyOperation(values, operators);
                }
                operators.push(expression[i++]);
            }
            else {
                cerr << "Warning: Unknown character '" << expression[i] << "' skipped." << endl;
                i++;
            }
        }

        while (!operators.empty()) {
            applyOperation(values, operators);
        }

        return values.empty() ? 0 : values.top();
    }

public:
    void processFileInput(const string& inputFile, const string& outputFile) {
        ifstream inFile(inputFile);
        ofstream outFile(outputFile);

        if (!inFile) {
            cerr << "Error: Unable to open input file: " << inputFile << endl;
            return;
        }

        if (!outFile) {
            cerr << "Error: Unable to open output file: " << outputFile << endl;
            return;
        }

        string expression;
        while (getline(inFile, expression)) {
            if (expression.empty()) continue;
            double result = processExpression(expression);
            outFile << "Expression: " << expression << " = " << result << endl;
        }

        inFile.close();
        outFile.close();
        cout << "✅ Processing complete. Check '" << outputFile << "' for results." << endl;
    }
};

int main() {
    Calculator calc;
    string inputFile = "input.txt";
    string outputFile = "output.txt";
    calc.processFileInput(inputFile, outputFile);
    return 0;
}