Why loop control is required in Go - See It in Action

Why loop control is required

📖 Scenario: Imagine you are organizing a small party and you have a list of guests. You want to greet each guest but stop greeting if you see a guest named "John" because he is running late and you want to wait for him before continuing.

🎯 Goal: You will create a program that loops through a list of guest names and stops the loop when it finds the name "John". This will teach you why controlling loops is important to avoid unnecessary work or to handle special cases.

📋 What You'll Learn

Create a slice of strings called guests with these exact names: "Alice", "Bob", "John", "Diana", "Eve"

Create a variable called stopName and set it to "John"

Use a for loop with index i and value guest to iterate over guests

Inside the loop, use an if statement to check if guest equals stopName and use break to stop the loop

Print "Greeting " followed by the guest's name for each guest greeted before stopping

💡 Why This Matters

🌍 Real World

Loop control is useful when you want to stop or skip parts of a loop based on conditions, like stopping a process when a special case happens.

💼 Career

Understanding loop control helps in writing efficient programs that do not waste time or resources by processing unnecessary data.

1

Create the guest list

Create a slice of strings called guests with these exact names: "Alice", "Bob", "John", "Diana", "Eve"

Go

# Create the guests slice with the exact names
# Your code here

Hint

Use guests := []string{} to create the list with the exact names inside curly braces.

2

Add the stop name variable

Create a variable called stopName and set it to "John"

Go

package main

func main() {
    guests := []string{"Alice", "Bob", "John", "Diana", "Eve"}
    // Create stopName variable with value "John"
    // Your code here
}

Hint

Use stopName := "John" to create the variable.

3

Loop through guests and stop at stopName

Use a for loop with index i and value guest to iterate over guests. Inside the loop, use an if statement to check if guest equals stopName and use break to stop the loop.

Go

package main

func main() {
    guests := []string{"Alice", "Bob", "John", "Diana", "Eve"}
    stopName := "John"

    // Loop through guests and stop when guest equals stopName
    // Your code here
}

Hint

Use for i, guest := range guests to loop. Use if guest == stopName and break inside the loop.

4

Print greetings before stopping

Inside the loop, print "Greeting " followed by the guest's name for each guest greeted before stopping. Use fmt.Println to print.

Go

package main

import "fmt"

func main() {
    guests := []string{"Alice", "Bob", "John", "Diana", "Eve"}
    stopName := "John"

    for i, guest := range guests {
        if guest == stopName {
            break
        }
        // Print greeting for guest
        // Your code here
    }
}

Hint

Use fmt.Println("Greeting", guest) inside the loop after the if check.

Practice

1. Why is loop control like break or continue required in Go loops?

easy

A. To print output inside the loop

B. To declare variables inside the loop

C. To define the loop variable type

D. To manage when to stop or skip parts of the loop

Solution

1. Step 1: Understand loop control purpose

   Loop control statements like break and continue help decide when to stop or skip parts of a loop.

2. Step 2: Identify correct usage

   They do not declare variables or print output; their role is to control loop flow.

3. Final Answer:

   To manage when to stop or skip parts of the loop -> Option D

4. Quick Check:

   Loop control = manage loop flow [OK]

Hint: Loop control changes loop flow, not variable types [OK]

Common Mistakes:

• Thinking loop control declares variables
• Confusing loop control with output commands
• Assuming loop control sets variable types

2. Which of the following is the correct syntax to skip the current iteration in a Go for loop?

easy

A. skip

B. break

C. continue

D. next

Solution

1. Step 1: Recall Go loop control keywords

   In Go, continue skips the current iteration and moves to the next.

2. Step 2: Differentiate from other keywords

   break stops the loop entirely; skip and next are not valid Go keywords.

3. Final Answer:

   continue -> Option C

4. Quick Check:

   Skip iteration = continue [OK]

Hint: Use continue to skip current loop iteration [OK]

Common Mistakes:

• Using break to skip iteration instead of stopping loop
• Using non-existent keywords like skip or next
• Confusing continue with break

3. What will be the output of this Go code?

for i := 1; i <= 5; i++ {
    if i == 3 {
        break
    }
    fmt.Print(i, " ")
}

medium

A. 1 2

B. 1 2 3 4 5

C. 3 4 5

D. 1 2 3

Solution

1. Step 1: Analyze loop and break condition

   The loop runs from 1 to 5, but breaks when i == 3.

2. Step 2: Determine printed values before break

   It prints values before break: 1 and 2, then stops at 3 without printing it.

3. Final Answer:

   1 2 -> Option A

4. Quick Check:

   Break stops loop at 3, prints before break [OK]

Hint: Break stops loop immediately, print before break only [OK]

Common Mistakes:

• Assuming break prints the break value
• Thinking loop continues after break
• Confusing break with continue

4. Identify the error in this Go loop code:

for i := 0; i < 5; i++ {
    if i == 2 {
        continue
    }
    fmt.Println(i)
    break
}

medium

A. The break is inside the loop, so loop stops after first iteration

B. continue is used incorrectly and causes syntax error

C. Loop variable i is not declared properly

D. fmt.Println is not allowed inside loops

Solution

1. Step 1: Understand loop flow with continue and break

   When i == 2, continue skips printing and break is after print, so loop stops after first iteration.

2. Step 2: Identify why loop stops early

   Break inside loop after print causes loop to stop immediately, so only one value prints.

3. Final Answer:

   The break is inside the loop, so loop stops after first iteration -> Option A

4. Quick Check:

   Break inside loop stops it early [OK]

Hint: Break inside loop stops all iterations immediately [OK]

Common Mistakes:

• Thinking continue causes syntax error
• Assuming break is outside loop
• Believing fmt.Println can't be inside loops

5. You want to print all numbers from 1 to 10 except multiples of 3 using a Go loop. Which code snippet correctly uses loop control to achieve this?

hard

A. for i := 1; i <= 10; i++ {
if i % 3 == 0 {
break
}
fmt.Println(i)
}

B. for i := 1; i <= 10; i++ {
if i % 3 == 0 {
continue
}
fmt.Println(i)
}

C. for i := 1; i <= 10; i++ {
if i % 3 == 0 {
fmt.Println(i)
}
}

D. for i := 1; i <= 10; i++ {
fmt.Println(i)
if i % 3 == 0 {
continue
}
}

Solution

1. Step 1: Understand the requirement

   We want to skip printing multiples of 3 but continue the loop for others.

2. Step 2: Analyze each option

   for i := 1; i <= 10; i++ { if i % 3 == 0 { break } fmt.Println(i) } breaks loop on multiples of 3, stopping early. for i := 1; i <= 10; i++ { if i % 3 == 0 { continue } fmt.Println(i) } uses continue to skip multiples of 3 correctly. for i := 1; i <= 10; i++ { if i % 3 == 0 { fmt.Println(i) } } prints only multiples of 3, wrong. for i := 1; i <= 10; i++ { fmt.Println(i) if i % 3 == 0 { continue } } prints all numbers including multiples of 3.

3. Final Answer:

   Option B code correctly skips multiples of 3 using continue -> Option B

4. Quick Check:

   Use continue to skip unwanted iterations [OK]

Hint: Use continue to skip unwanted loop iterations [OK]

Common Mistakes:

• Using break instead of continue stops loop early
• Printing only multiples instead of skipping them
• Placing continue after print causing unwanted output