Dart Functions

1. What is a Function? (Programming Definition)

A function is a block of code designed to perform a specific task. Functions help organize code into reusable pieces that can be called whenever needed. They can take inputs, called parameters, and often return a result.

2. What is a Function? (Real-World Example)

Imagine a coffee machine. You press a button, and it makes coffee for you. The coffee machine is like a function — it performs a specific task when you "call" it (press the button). You might tell it what kind of coffee you want (input), and it gives you a cup of coffee (output).

3. Syntax of a Simple Function in Dart

void sayHello() {
  print("Hello!");
}

This function sayHello prints the word "Hello!" when called.

4. Calling a Function

void main() {
  sayHello();  // Calling the function to execute its code
}

void sayHello() {
  print("Hello!");
}

When sayHello() is called inside main(), it runs and prints "Hello!" to the screen.

5. Functions with Parameters

Functions can take inputs (parameters) to work with different data.

void greet(String name) {
  print("Hello, $name!");
}

void main() {
  greet("Alex");
  greet("Samantha");
}

Here, the function greet takes a String called name and prints a personalized greeting.

6. Functions that Return Values

Functions can also return a value after doing some work.

int add(int a, int b) {
  return a + b;
}

void main() {
  int sum = add(5, 3);
  print("Sum is $sum");
}

The add function adds two numbers and returns the result.

7. Real-World Example: Calculator Function

Think of a calculator: you give it two numbers and the operation (add, subtract), and it returns the result.

double calculate(double num1, double num2, String operation) {
  if (operation == "add") {
    return num1 + num2;
  } else if (operation == "subtract") {
    return num1 - num2;
  } else {
    return 0;
  }
}

void main() {
  print(calculate(10, 5, "add"));      // Output: 15
  print(calculate(10, 5, "subtract")); // Output: 5
}