Closures and Higher-Order Functions

Closures and Higher-Order Functions

In this lesson — part of Advanced Features — you'll learn closures and higher-order functions in PowerShell and why it matters in real work.

Why it matters

Functions that take or return functions unlock concise, composable code.

Key ideas

• Functions as values
• map / filter / reduce
• Callbacks
• Composition

In practice

Here's how it looks in idiomatic PowerShell:

function Invoke-Twice {
    param([scriptblock]$Action, $Value)
    & $Action $Value
    & $Action $Value
}
$double = { param($x) $x * 2 }
Invoke-Twice -Action $double -Value 5      # 10, 10

1..3 | ForEach-Object $double              # pass a scriptblock as the transform
[Func[int,int]]$f = { param($x) $x + 1 }   # interop with .NET delegates

PowerShell note: Script blocks ({ }) are first-class values you store in variables and invoke with the call operator (&), and they implicitly convert to .NET delegate types like Func<T> for interop with framework APIs.

Try it yourself

Exercise: In PowerShell, use map and filter to get the squares of the even numbers.

Recap

You now understand closures and higher-order functions and can apply it in PowerShell. Mark this lesson complete and continue to the next one.