feat: Implement C++ Currency Converter

Added a C++ Currency Converter feature with OOP-based design, supporting multi-currency
conversion, user-friendly console interface, and error handling.

Closes #4

Author: Satvik-Singh192

Src/Currency_Converter/CurrencyConverter.cpp

@@ -0,0 +1,55 @@
+#include "CurrencyConverter.h"
+#include <iostream>
+#include <stdexcept> 
+
+CurrencyConverter::CurrencyConverter() {
+    // We will use USD as the "base currency" for all conversions.
+    // These rates represent how many USD 1 unit of the currency is worth.
+    // Example: 1 EUR = 1.08 USD
+    rates["USD"] = 1.00;
+    rates["EUR"] = 1.08;
+    rates["INR"] = 0.012;
+    rates["GBP"] = 1.25;
+    rates["JPY"] = 0.0067; 
+}
+
+bool CurrencyConverter::isCurrencySupported(const std::string& currencyCode) {
+    return rates.find(currencyCode) != rates.end();
+}
+
+// Helper function to print all supported currency codes
+void CurrencyConverter::printAvailableCurrencies() {
+    std::cout << "Supported currencies: ";
+    for (const auto& pair : rates) {
+        std::cout << pair.first << " "; // pair.first is the key (e.g., "USD")
+    }
+    std::cout << std::endl;
+}
+
+// The main conversion logic
+double CurrencyConverter::convert(double amount, const std::string& fromCurrency, const std::string& toCurrency) {
+    
+    // 1. Error Handling: Check if both currencies are supported
+    if (!isCurrencySupported(fromCurrency)) {
+        throw std::invalid_argument("Error: 'From' currency code not supported: " + fromCurrency);
+    }
+    if (!isCurrencySupported(toCurrency)) {
+        throw std::invalid_argument("Error: 'To' currency code not supported: " + toCurrency);
+    }
+
+    // 2. Handle simple case: No conversion needed
+    if (fromCurrency == toCurrency) {
+        return amount;
+    }
+
+    // 3. Conversion Logic (using USD as a base)
+    // First, convert the 'from' amount into our base currency (USD)
+    double amountInUSD = amount * rates[fromCurrency];
+
+    // Second, convert from USD into the 'to' currency
+    // (We divide because the rate is X_USD = 1_TARGET_CURRENCY)
+    // To get 1 USD = Y_TARGET_CURRENCY, we do 1 / rate.
+    double finalAmount = amountInUSD / rates[toCurrency];
+
+    return finalAmount;
+}

Src/Currency_Converter/CurrencyConverter.h

@@ -0,0 +1,26 @@
+#pragma once 
+#include <string>
+#include <map>
+
+class CurrencyConverter {
+private:
+    // A map to store exchange rates, with USD as the base currency.
+    // The key is the currency code (e.g., "EUR"), and the value is
+    // how many USD 1 unit of that currency is worth.
+    std::map<std::string, double> rates;
+
+public:
+    // This is the constructor. It's called when you create a new
+    // CurrencyConverter object. We use it to load our predefined rates.
+    CurrencyConverter();
+
+    // The main conversion function.
+    // Throws an exception if a currency code is invalid.
+    double convert(double amount, const std::string& fromCurrency, const std::string& toCurrency);
+
+    // A helper function to check if we support a currency.
+    bool isCurrencySupported(const std::string& currencyCode);
+
+    // A helper function to show the user what currencies are available.
+    void printAvailableCurrencies();
+};

Src/Currency_Converter/README.md

@@ -25,3 +25,48 @@ The program is designed using **Object-Oriented Programming (OOP)** principles,
   - Clear and readable methods  
 
 ---
+
+# How to Compile and Run
+
+## Prerequisites
+You will need a C++ compiler installed on your system, such as **g++** (part of the **MinGW-w64** toolset on Windows) or **Clang**.  
+Make sure it is added to your system's **PATH**.
+
+---
+
+## Steps
+
+1. **Open your terminal or command prompt.**
+
+2. **Navigate to the project directory** where the `.cpp` files are located:
+
+   ```bash
+   cd path/to/Currency_Converter
+  ```
+
+3. **Compile and Run**
+  # Compile the source code
+  Run the following command in your terminal:
+
+  ```bash
+  g++ main.cpp CurrencyConverter.cpp -o currency_converter -std=c++11
+  ```
+
+This will compile all the necessary files and create a single executable program named  
+`currency_converter` (or `currency_converter.exe` on Windows).
+
+---
+
+  # Run the Application
+
+  **On Windows (PowerShell/CMD):**
+  ```bash
+  .\currency_converter.exe
+  ```
+
+  **On macOS or Linux:**
+  ```bash
+  ./currency_converter
+  ```
+
+Follow the on-screen prompts to use the converter.

Src/Currency_Converter/currency_converter.exe

@@ -0,0 +1,89 @@
+#include <iostream>
+#include <string>
+#include <limits>   
+#include <stdexcept>  
+
+#include "CurrencyConverter.h"
+
+double getValidAmount() {
+    double amount;
+    while (true) {
+        std::cout << "Enter amount to convert: ";
+        if (std::cin >> amount) {
+            if (amount > 0) {
+                return amount;
+            } else {
+                std::cout << "Please enter a positive amount." << std::endl;
+            }
+        } else {
+            // This handles non-numeric input
+            std::cout << "Invalid input. Please enter a number." << std::endl;
+            std::cin.clear(); // Clear the error flag
+            // Discard the invalid input from the buffer
+            std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
+        }
+    }
+}
+
+// Helper function to get a valid currency code from the user
+std::string getValidCurrency(const std::string& prompt, CurrencyConverter& converter) {
+    std::string code;
+    while (true) {
+        std::cout << prompt;
+        std::cin >> code;
+        
+        // Convert input to uppercase to be safe
+        for (auto &c : code) c = toupper(c);
+
+        if (converter.isCurrencySupported(code)) {
+            return code; // Valid currency
+        } else {
+            std::cout << "Invalid or unsupported currency code. Please try again." << std::endl;
+            converter.printAvailableCurrencies();
+        }
+    }
+}
+
+
+int main() {
+    // 1. Create an instance of our converter.
+    // This calls the constructor and loads the rates.
+    CurrencyConverter converter;
+
+    std::cout << "Welcome to the C++ Currency Converter!" << std::endl;
+
+    // 2. Main application loop
+    while (true) {
+        std::cout << "\n------------------------------------" << std::endl;
+        converter.printAvailableCurrencies();
+
+        // 3. Get all user inputs
+        std::string from = getValidCurrency("Convert FROM (e.g., USD): ", converter);
+        std::string to = getValidCurrency("Convert TO (e.g., EUR): ", converter);
+        double amount = getValidAmount();
+
+        // 4. Perform conversion and handle errors
+        try {
+            double result = converter.convert(amount, from, to);
+            
+            // Print the result
+            std::cout << "\n--- Result ---" << std::endl;
+            std::cout << amount << " " << from << " = " << result << " " << to << std::endl;
+        
+        } catch (const std::exception& e) {
+            // This will catch errors we threw in our .convert() function
+            std::cout << e.what() << std::endl;
+        }
+
+        // 5. Ask to go again
+        std::cout << "\nDo you want to perform another conversion? (y/n): ";
+        char choice;
+        std::cin >> choice;
+        if (choice != 'y' && choice != 'Y') {
+            break; // Exit the while loop
+        }
+    }
+
+    std::cout << "Thank you for using the converter. Goodbye!" << std::endl;
+    return 0;
+}