Creating a Simple Command-Line Application

This example creates a simple command-line calculator.

import 'dart:io';

double add(double a, double b) => a + b;
double subtract(double a, double b) => a - b;
double multiply(double a, double b) => a * b;
double divide(double a, double b) {
  if (b == 0) {
    throw Exception('Cannot divide by zero');
  }
  return a / b;
}

void main() {
  print('Simple Calculator');
  print('Enter two numbers:');
  
  var input1 = stdin.readLineSync();
  var input2 = stdin.readLineSync();
  
  double num1 = double.parse(input1!);
  double num2 = double.parse(input2!);
  
  print('Choose an operation: +, -, *, /');
  var operation = stdin.readLineSync();
  
  double result;
  switch (operation) {
    case '+':
      result = add(num1, num2);
      break;
    case '-':
      result = subtract(num1, num2);
      break;
    case '*':
      result = multiply(num1, num2);
      break;
    case '/':
      result = divide(num1, num2);
      break;
    default:
      print('Invalid operation');
      return;
  }
  
  print('Result: $result');
}