Problem Statement

Create a list of ten functions, in the simplest manner possible   (anonymous functions are encouraged),   such that the function at index   i   (you may choose to start   i   from either   0   or   1),   when run, should return the square of the index,   that is,   i 2. Display the result of running any but the last function, to demonstrate that the function indeed remembers its value.

Demonstrate how to create a series of independent closures based on the same template but maintain separate copies of the variable closed over. In imperative languages, one would generally use a loop with a mutable counter variable. For each function to maintain the correct number, it has to capture the value of the variable at the time it was created, rather than just a reference to the variable, which would have a different value by the time the function was run. See also: Multiple distinct objects

Let's start with the solution:

function Get-Closure ([double]$Number)
{
    {param([double]$Sum) return $script:Number *= $Sum}.GetNewClosure()
}


for ($i = 1; $i -lt 11; $i++)
{ 
    $total = Get-Closure -Number $i

    [PSCustomObject]@{
        Function = $i
        Sum      = & $total -Sum $i
    }
}


$numbers = 1..20 | Get-Random -Count 10

foreach ($number in $numbers)
{
    $total = Get-Closure -Number $number

    [PSCustomObject]@{
        Function = $number
        Sum      = & $total -Sum $number
    }
}