Zero values in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an integer variable with its zero value.

Go

var num [1]

Drag options to blanks, or click blank then click option'

Aint

Bstring

Cbool

Dfloat64

Attempts:

3 left

💡 Hint

Common Mistakes

Using string type instead of int.

Using bool type which defaults to false, not zero integer.

In Go, declaring a variable with type int without initialization sets it to zero value 0.

2fill in blank

medium

Complete the code to declare a boolean variable with its zero value.

Go

var flag [1]

Drag options to blanks, or click blank then click option'

Astring

Bint

Cbool

Dfloat64

Attempts:

3 left

💡 Hint

Common Mistakes

Using int type instead of bool.

Using string type which defaults to empty string, not false.

Boolean variables in Go default to false as their zero value.

3fill in blank

hard

Fix the error in the code by completing the variable declaration with the correct zero value type.

Go

var name [1]

Drag options to blanks, or click blank then click option'

Afloat64

Bbool

Cint

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or bool types for string data.

Forgetting to specify the type.

Strings in Go default to an empty string "" as their zero value.

4fill in blank

hard

Fill both blanks to declare a float64 variable and assign its zero value.

Go

var price [1] = [2]

Drag options to blanks, or click blank then click option'

Afloat64

B0.0

C0

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using int type for floating point numbers.

Assigning zero as integer 0 instead of 0.0.

Float64 variables use type float64 and their zero value is 0.0.

5fill in blank

hard

Fill all three blanks to declare a slice of strings with its zero value.

Go

var fruits [1] [2] [3]

Drag options to blanks, or click blank then click option'

A[]string

Bnil

C=

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using string instead of []string for slice.

Not assigning nil explicitly.

Using wrong assignment operator.

A slice of strings is declared as []string. Its zero value is nil, assigned with =.

Practice

1. What is the zero value of an int variable in Go?

easy

A. "" (empty string)

B. nil

C. 0

D. false

Solution

1. Step 1: Understand zero values for basic types

   In Go, each type has a default zero value when not initialized.

2. Step 2: Identify zero value for int type

   The zero value for int is the number 0.

3. Final Answer:

   0 -> Option C

4. Quick Check:

   int zero value = 0 [OK]

Hint: Remember: int zero value is always 0 [OK]

Common Mistakes:

• Confusing int zero value with nil
• Thinking zero value is empty string
• Mixing boolean zero value with int

2. Which of the following is the correct way to declare a variable with its zero value in Go?

easy

A. var x int = false

B. var x int = nil

C. var x int = ""

D. var x int

Solution

1. Step 1: Recall Go variable declaration syntax

   Declaring a variable without initialization sets it to its zero value.

2. Step 2: Check each option for correctness

   var x int declares x as int without initialization, so it gets zero value 0. Other options assign invalid values for int.

3. Final Answer:

   var x int -> Option D

4. Quick Check:

   Declare without init = zero value [OK]

Hint: Declare without assignment to get zero value [OK]

Common Mistakes:

• Assigning nil to int
• Assigning string to int
• Assigning boolean to int

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

package main
import "fmt"
func main() {
    var b bool
    fmt.Println(b)
}

medium

A. false

B. Compilation error

C. nil

D. true

Solution

1. Step 1: Identify the variable type and initialization

   Variable b is declared as bool without explicit initialization.

2. Step 2: Recall zero value for bool type

   The zero value for bool is false, so b is false by default.

3. Final Answer:

   false -> Option A

4. Quick Check:

   bool zero value = false [OK]

Hint: Uninitialized bool defaults to false [OK]

Common Mistakes:

• Expecting true as default
• Thinking nil is valid bool
• Assuming compilation error

4. Identify the error in this Go code snippet related to zero values:

package main
func main() {
    var s string = nil
}

medium

A. Assigning nil to string causes a compile error

B. String zero value should be 0

C. Variable s should be declared as int

D. No error, code runs fine

Solution

1. Step 1: Understand zero value for string type

   Zero value for string is an empty string "", not nil.

2. Step 2: Check assignment validity

   Assigning nil to a string variable causes a compile-time error because nil is not a valid string value.

3. Final Answer:

   Assigning nil to string causes a compile error -> Option A

4. Quick Check:

   string zero value = "" not nil [OK]

Hint: Strings cannot be nil, use empty string "" [OK]

Common Mistakes:

• Using nil for string
• Confusing zero value with nil
• Ignoring compile errors

5. You want to create a map in Go that stores string keys and integer values. You declare it as:

var m map[string]int

What is the zero value of m and what must you do before adding elements?

hard

A. m is zero; no initialization needed, just assign values

B. m is nil; you must initialize it with make before adding elements

C. m is an empty map; you can add elements immediately

D. m is a map with default zero values for keys and values

Solution

1. Step 1: Identify zero value of map type

   Maps declared without initialization have zero value nil.

2. Step 2: Understand map usage requirements

   You cannot add elements to a nil map; you must initialize it using make(map[string]int) before adding keys and values.

3. Final Answer:

   m is nil; you must initialize it with make before adding elements -> Option B

4. Quick Check:

   Maps zero value = nil; initialize with make [OK]

Hint: Maps start nil; use make() before adding keys [OK]

Common Mistakes:

• Trying to add to nil map
• Assuming map is empty but usable
• Confusing zero value with empty map