Default parameter values in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this PowerShell function call?

Consider this PowerShell function with a default parameter value:

function Greet($name = 'Guest') { Write-Output "Hello, $name!" }

What will be the output of Greet when called without arguments?

PowerShell

function Greet($name = 'Guest') { Write-Output "Hello, $name!" }
Greet

A Error: Missing argument for parameter 'name'

B Hello, Guest!

C Hello, $name!

D Hello, !

💡 Hint

Think about what happens when you call a function without providing a value for a parameter that has a default.

The function Greet has a default value 'Guest' for the parameter $name. When called without arguments, it uses this default and outputs "Hello, Guest!".

📝 Syntax

intermediate

Which option correctly defines a parameter with a default value in PowerShell?

Choose the correct syntax to define a function parameter $count with a default value of 5.

A param([int]$count <- 5)

B param([int]$count:5)

C param([int]$count => 5)

D param([int]$count = 5)

💡 Hint

PowerShell uses the equals sign = to assign default values to parameters.

The correct syntax to assign a default value to a parameter in PowerShell is param([type]$paramName = defaultValue). Options A, B, and D use invalid syntax.

🔧 Debug

advanced

Why does this PowerShell function throw an error when called without arguments?

Look at this function:

function Show-Info {
  param(
    [Parameter(Mandatory=$true)]
    [string]$name,
    [int]$age = 30
  )
  Write-Output "$name is $age years old."
}

Show-Info

Why does calling Show-Info without arguments cause an error?

PowerShell

function Show-Info {
  param(
    [Parameter(Mandatory=$true)]
    [string]$name,
    [int]$age = 30
  )
  Write-Output "$name is $age years old."
}

Show-Info

A Because $name has no default value and is required, so calling without it causes an error.

B Because $age has a default value, but $name must be an integer.

C Because the function syntax is invalid; default values must be last parameters.

D Because Write-Output cannot handle variables without explicit values.

💡 Hint

Check which parameters have default values and which do not.

The parameter $name has no default value, so it is required. Calling the function without providing $name causes an error. The parameter $age has a default value and is optional.

🚀 Application

advanced

What is the output of this script using default parameter values?

Given this PowerShell script:

function Calculate-Sum {
  param(
    [int]$a = 10,
    [int]$b = 20
  )
  return $a + $b
}

$result1 = Calculate-Sum
$result2 = Calculate-Sum -a 5
$result3 = Calculate-Sum -b 15
$result4 = Calculate-Sum -a 3 -b 7

Write-Output "$result1,$result2,$result3,$result4"

What will be the output?

PowerShell

function Calculate-Sum {
  param(
    [int]$a = 10,
    [int]$b = 20
  )
  return $a + $b
}

$result1 = Calculate-Sum
$result2 = Calculate-Sum -a 5
$result3 = Calculate-Sum -b 15
$result4 = Calculate-Sum -a 3 -b 7

Write-Output "$result1,$result2,$result3,$result4"

A 30,25,25,10

B 30,25,35,10

C 30,25,30,10

D 30,15,25,10

💡 Hint

Remember that parameters with default values use those defaults if not provided.

Calculations:
- $result1: defaults 10 + 20 = 30
- $result2: 5 + default 20 = 25
- $result3: default 10 + 15 = 25
- $result4: 3 + 7 = 10

🧠 Conceptual

expert

How does PowerShell handle default parameter values when using splatting?

Consider this function:

function Show-Message {
  param(
    [string]$text = 'Hello',
    [string]$color = 'Blue'
  )
  Write-Output "$text in $color"
}

And this splatting call:

$params = @{ text = 'Hi' }
Show-Message @params

What will be the output and why?

PowerShell

function Show-Message {
  param(
    [string]$text = 'Hello',
    [string]$color = 'Blue'
  )
  Write-Output "$text in $color"
}

$params = @{ text = 'Hi' }
Show-Message @params

A Hello in Blue - because splatting ignores default values.

B Hi in - because $color is empty when not passed in splatting.

C Hi in Blue - because $color uses its default value when not provided in splatting.

D Error - because splatting requires all parameters to be specified.

💡 Hint

Think about how splatting passes only specified parameters and how defaults fill in missing ones.

Splatting passes only the text parameter with value 'Hi'. The color parameter is not passed, so PowerShell uses its default 'Blue'. The output is "Hi in Blue".

Practice

1. What is the main purpose of using default parameter values in a PowerShell function?

easy

A. To make the function run faster

B. To force the user to always provide a value

C. To provide fallback values when no argument is passed

D. To disable the function if parameters are missing

Solution

1. Step 1: Understand default parameter values

   Default parameter values are set to be used when no argument is provided by the user.

2. Step 2: Identify the purpose

   This helps the function run smoothly without errors by using fallback values.

3. Final Answer:

   To provide fallback values when no argument is passed -> Option C

4. Quick Check:

   Default values = fallback values [OK]

Hint: Defaults fill in missing inputs automatically [OK]

Common Mistakes:

• Thinking defaults speed up execution
• Believing defaults force user input
• Assuming defaults disable functions

2. Which of the following is the correct syntax to set a default value of 10 for a parameter named $count in a PowerShell function?

easy

A. param([int]$count <- 10)

B. param([int]$count = 10)

C. param([int]$count : 10)

D. param([int]$count => 10)

Solution

1. Step 1: Recall PowerShell parameter default syntax

   PowerShell uses the equals sign (=) to assign default values in parameters.

2. Step 2: Match syntax to options

   Only param([int]$count = 10) uses = correctly to assign 10 as default.

3. Final Answer:

   param([int]$count = 10) -> Option B

4. Quick Check:

   Default assignment uses = in PowerShell [OK]

Hint: Use = to assign default values in param block [OK]

Common Mistakes:

• Using : or => instead of = for defaults
• Confusing syntax with other languages
• Placing default outside param block

3. What will be the output of this PowerShell function call?

function Greet { param([string]$name = "Guest") "Hello, $name!" }
Greet

medium

A. Hello, Guest!

B. Hello, !

C. Hello, $name!

D. Error: Missing argument

Solution

1. Step 1: Analyze function parameter default

   The parameter $name has a default value "Guest" if no argument is passed.

2. Step 2: Check function call without argument

   Calling Greet without arguments uses the default "Guest".

3. Final Answer:

   Hello, Guest! -> Option A

4. Quick Check:

   Default used when no argument given = Hello, Guest! [OK]

Hint: No argument? Default value is used [OK]

Common Mistakes:

• Expecting empty string output
• Thinking variable name prints literally
• Assuming error on missing argument

4. Identify the error in this PowerShell function definition:

function Show-Info {
 param([string]$info =)
 Write-Output $info
}

medium

A. Missing default value after =

B. Parameter type [string] is invalid

C. Write-Output cannot be used inside functions

D. Function name cannot contain a hyphen

Solution

1. Step 1: Check parameter default syntax

   The parameter $info has an equals sign but no value after it, which is invalid.

2. Step 2: Validate other parts

   Parameter type [string] is valid, Write-Output is allowed, and hyphens are allowed in function names.

3. Final Answer:

   Missing default value after = -> Option A

4. Quick Check:

   Default value must follow = [OK]

Hint: Default values must not be empty after = [OK]

Common Mistakes:

• Leaving = without a value
• Misunderstanding function name rules
• Thinking Write-Output is disallowed

5. You want a PowerShell function Calculate-Sum that adds two numbers, but if the second number is not provided, it should default to the first number. Which parameter default setup achieves this?

hard

A. param([int]$a, [int]$b = 0)

B. param([int]$a = 0, [int]$b = 0)

C. param([int]$a, [int]$b = $null)

D. param([int]$a, [int]$b = $a)

Solution

1. Step 1: Understand PowerShell parameter default evaluation

   PowerShell binds earlier parameters before evaluating defaults for later ones, allowing references to prior parameters.

2. Step 2: Identify the correct setup

   param([int]$a, [int]$b = $a) sets $b to the value of $a when $b is not provided.

3. Final Answer:

   param([int]$a, [int]$b = $a) -> Option D

4. Quick Check:

   Later defaults can reference earlier parameters [OK]

Hint: Later parameters can default using earlier parameter values [OK]

Common Mistakes:

• Using fixed defaults like 0 or $null
• Thinking parameter references are not allowed in defaults
• Assuming defaults must be literal constants