📘 Class 21 – Expressions, Anonymous Functions & IIFE in Go

🎥 Video Name:

Anonymous function, Expression & IIFE

📦 Code Written in This Class

// Anonymous function
// IIFE - Immediately Invoked Function Expression

package main

import "fmt"

func main() {
	// Anonymous function
	func(a int, b int) {
		c := a + b
		fmt.Println(c)
	}(5, 7) // IIFE
}

func init() {
	fmt.Println("I'll be called first")
}

🧠 Key Concepts

🧮 Expression in Go

An expression is any snippet of code that evaluates to a value.

Examples:

a + b          // is an expression
func(x, y){}   // is a function expression

Expressions can be used as values, passed around, or even executed immediately — which leads us to…

🧙 Anonymous Function

An anonymous function is a function without a name.

Instead of:

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

You write:

func(a, b int) int {
	return a + b
}

✅ You can assign it to a variable, pass it as an argument, or invoke it on the spot.

⚡ IIFE (Immediately Invoked Function Expression)

An IIFE is an anonymous function that is executed immediately right after it's defined.

Syntax:

func(a int, b int) {
	// do stuff
}(5, 7)

Use-case: You want to run a small block of logic immediately, without polluting the namespace with a new function name.

🖥️ CLI-style Execution Visualization

=========== Compilation Phase =============
Found init() ✅
Found main() ✅

=========== Execution Phase ===============

🔁 init() runs first
→ Prints: I'll be called first

🧠 Data Segment:
(No global vars in this case)

📚 Stack Frame:
┌─────────────────────┐
│    main()           │
│ ┌─────────────────┐ │
│ │  anonymous func │ │
│ └─────────────────┘ │
└─────────────────────┘

main() calls an IIFE:
→ Passes 5 and 7
→ Inside IIFE: c := 5 + 7 = 12
→ Prints: 12

=========== Execution Complete =============

🧵 TL;DR

-[] ✅ Expressions return values and can be assigned or executed.

-[] 🧪 Anonymous functions have no name, great for quick logic blocks.

-[] 🚀 IIFE: Define & execute in one go. Great for one-off logic.