📘 exercises.md

Chapter 2 – Exercises

Functions, Structs & Packages

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🟢 Basic Level

Exercise 1 – Simple Function

Write a function Multiply(a int, b int) int that returns the product of two integers.

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Exercise 2 – Multiple Return Values

Write a function SafeDivide(a int, b int) (int, error) Return an error if b == 0.

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Exercise 3 – Struct Creation

Create a struct Book with fields:

• Title (string)
• Author (string)
• Price (float64)

Create one instance and print it.

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Exercise 4 – Method on Struct

Add a method to Book:

Discount(percent float64)

It should reduce the price accordingly.

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Exercise 5 – Value vs Pointer Receiver

Modify Exercise 4 so that:

• One version uses value receiver
• One version uses pointer receiver

Observe the difference.

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🟡 Intermediate Level

Exercise 6 – Constructor Pattern

Create a constructor:

NewBook(title string, author string, price float64) *Book

Ensure price cannot be negative.

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Exercise 7 – Validation Method

Add a method:

IsExpensive() bool

Return true if price > 1000.

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Exercise 8 – Struct Composition

Create:

type Address struct {
    City string
    Country string
}

Embed it inside:

type Customer struct {
    Name string
    Address
}

Create a sample customer.

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Exercise 9 – Package Organization

Move Book into its own package called library.

Use it in main.go.

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Exercise 10 – Zero Value Safety

Create a User struct with:

• Name
• Age

Write a method IsValid() that returns false if zero values are detected.

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🔵 Advanced Level

Exercise 11 – Function as Parameter

Create a function:

ApplyOperation(a int, b int, op func(int, int) int) int

Test with addition and multiplication.

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Exercise 12 – Interface Preparation

Define an interface:

type Printable interface {
    Print() string
}

Make Book implement it.

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Exercise 13 – Struct Method Returning Error

Add a method to Book:

UpdatePrice(newPrice float64) error

Return error if price is negative.

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Exercise 14 – Slice of Structs

Create a slice of Book. Write a function:

TotalPrice(books []Book) float64

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Exercise 15 – Pointer Semantics

Create a function:

IncreaseAllPrices(books []Book, percent float64)

Observe if changes persist. Fix it properly.

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Exercise 16 – Encapsulation Practice

Make the price field unexported. Create getter and setter methods.

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Exercise 17 – Method Chaining

Modify setter methods to return pointer to struct for chaining.

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Exercise 18 – Factory Logic

Create a function:

NewPremiumBook(...)

It automatically marks a boolean Premium = true.

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Exercise 19 – Small Refactor

Refactor code so:

• No direct struct field access outside package
• All modification via methods

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Exercise 20 – Mini Design Task

Design a Cart struct:

• AddBook()
• RemoveBook()
• TotalAmount()

Organize cleanly inside a package.

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