Short variable declaration in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare and initialize variable x with value 10 using short variable declaration.

Go

func main() {
    [1] := 10
    fmt.Println(x)
}

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

Avar x

Bx

Cint x

Dx var

Attempts:

3 left

💡 Hint

Common Mistakes

Using var keyword with := operator causes syntax error.

Trying to declare type explicitly with short declaration is invalid.

In Go, short variable declaration uses the syntax name := value. So x := 10 declares and initializes x with 10.

2fill in blank

medium

Complete the code to declare two variables a and b with values 5 and 7 using short variable declaration.

Go

func main() {
    [1] := 5, 7
    fmt.Println(a, b)
}

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

A(a, b)

Bvar a, b

Ca, b

D[a, b]

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses or brackets around variable names is invalid.

Using var keyword with := causes syntax error.

To declare multiple variables with short declaration, list their names separated by commas before :=.

3fill in blank

hard

Fix the error in the short variable declaration of count with value 100.

Go

func main() {
    [1] 100
    fmt.Println(count)
}

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

Avar count =

Bvar count :=

Ccount :

Dcount :=

Attempts:

3 left

💡 Hint

Common Mistakes

Using var keyword with := causes syntax error.

Using = instead of := for short declaration.

Short variable declaration uses := without var keyword. So count := 100 is correct.

4fill in blank

hard

Fill both blanks to declare variables name and age with values "Alice" and 30 using short variable declaration.

Go

func main() {
    [1] := "Alice"
    [2] := 30
    fmt.Println(name, age)
}

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

Aname

Bage

Cvar

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to declare both variables in one statement with commas.

Using var keyword with := operator.

Each variable must be declared separately with short declaration syntax: name := "Alice" and age := 30.

5fill in blank

hard

Fill all three blanks to declare variables width, height, and area where width and height are 5 and 10, and area is their product using short variable declaration.

Go

func main() {
    [1] := 5
    [2] := 10
    [3] := [1] * [2]
    fmt.Println(area)
}

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

Awidth

Bheight

Carea

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names in declaration.

Trying to declare multiple variables in one line incorrectly.

Declare width and height with short declaration, then declare area as their product.

Practice

1. What does the short variable declaration := do in Go?

easy

A. It assigns a value to an already declared variable outside a function.

B. It declares and initializes a new variable inside a function.

C. It declares a variable without initializing it.

D. It declares a global variable accessible everywhere.

Solution

1. Step 1: Understand short variable declaration usage

   The := syntax declares and initializes a variable in one step inside functions.

2. Step 2: Differentiate from other declarations

   It cannot be used without initialization or outside functions for global variables.

3. Final Answer:

   It declares and initializes a new variable inside a function. -> Option B

4. Quick Check:

   Short declaration = declare + initialize [OK]

Hint: Remember := means declare and assign inside functions [OK]

Common Mistakes:

• Thinking := works outside functions
• Using := without initializing
• Confusing := with simple assignment =

2. Which of the following is the correct way to declare and initialize a variable using short variable declaration in Go?

easy

A. x =: 10

B. var x := 10

C. x := 10

D. x :== 10

Solution

1. Step 1: Identify correct short declaration syntax

   The correct syntax is variable := value without the var keyword.

2. Step 2: Check each option

   x := 10 matches the correct syntax. The other options have invalid syntax.

3. Final Answer:

   x := 10 -> Option C

4. Quick Check:

   Short declaration syntax = variable := value [OK]

Hint: Short declaration never uses 'var' keyword [OK]

Common Mistakes:

• Adding 'var' with :=
• Swapping := to =:
• Using double equals or colons

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

func main() {
    a := 5
    a := 10
    fmt.Println(a)
}

medium

A. Compilation error

B. 10

C. 5

D. 0

Solution

1. Step 1: Analyze variable redeclaration

   Using a := 5 then a := 10 in the same scope causes redeclaration error.

2. Step 2: Understand Go's redeclaration rules

   Short declaration requires at least one new variable; here a is redeclared without new variables, causing error.

3. Final Answer:

   Compilation error -> Option A

4. Quick Check:

   Redeclaring same var with := in same scope = error [OK]

Hint: Short declaration needs at least one new variable [OK]

Common Mistakes:

• Assuming redeclaration overwrites variable
• Expecting last value to print
• Ignoring scope rules

4. Identify the error in this Go code snippet:

func main() {
    x := 10
    x := 20
    fmt.Println(x)
}

medium

A. x is redeclared in the same scope causing a compile error.

B. x is not initialized before use.

C. fmt.Println is used incorrectly.

D. No error, output will be 20.

Solution

1. Step 1: Check variable redeclaration

   The variable x is declared twice with := in the same function scope, which is not allowed.

2. Step 2: Understand Go's redeclaration rules

   Redeclaring a variable with := requires at least one new variable; here none is new, so compile error occurs.

3. Final Answer:

   x is redeclared in the same scope causing a compile error. -> Option A

4. Quick Check:

   Redeclaration without new vars = compile error [OK]

Hint: Redeclare only if at least one new variable appears [OK]

Common Mistakes:

• Thinking redeclaration updates variable silently
• Ignoring compile errors on redeclaration
• Assuming output prints last assigned value

5. Given the code below, which line correctly uses short variable declaration to add a new variable c while updating a?

func main() {
    a := 1
    b := 2
    // Insert line here
    fmt.Println(a, b, c)
}

hard

A. a, b := 3, 4

B. a := 3; c := 4

C. c := 4

D. a, c := 3, 4

Solution

1. Step 1: Understand short declaration with existing variables

   To update a and declare new c in one line, use a, c := 3, 4.

2. Step 2: Check other options

   a, b := 3, 4 redeclares two existing variables without a new one, causing a compile error. a := 3; c := 4 redeclares existing a without a new variable (compile error). c := 4 declares c without updating a.

3. Final Answer:

   a, c := 3, 4 -> Option D

4. Quick Check:

   Short declaration updates existing + new vars = correct [OK]

Hint: Use := with at least one new variable to update and declare [OK]

Common Mistakes:

• Trying to redeclare only existing vars with :=
• Declaring new vars separately without updating existing
• Forgetting to include new variable in declaration