rePS

0.1.0

Exercises/Advanced/adv-return-list/exercise.psd1

                                @{

    Id           = 'adv-return-list'

    Title        = 'Return a collection intact'

    Topic        = 'Advanced'

    Level        = 3

    Platforms    = @('Windows', 'Linux', 'MacOS')

    Tags         = @('collections', 'unrolling', 'generics', 'performance')

    FunctionName = 'Get-NumberList'

    Author       = 'rePS'

    Prompt       = @'

Write Get-NumberList so it builds a [System.Collections.Generic.List[int]]

containing 1..-Count and returns THE LIST ITSELF as a single object.

Use .Add() rather than += on an array (+= copies the whole array every time).

Watch out: PowerShell unrolls collections written to the output, so a naive

"return $list" gives the caller loose ints, or $null for an empty list.

    $list = Get-NumberList -Count 3

    $list.GetType().Name   # List`1

    (Get-NumberList -Count 0).Count   # 0, and the result is not $null

'@

    Hints        = @(

        '$list = [System.Collections.Generic.List[int]]::new(), then $list.Add($i) inside a loop.'

        'Write-Output -NoEnumerate -InputObject $list writes the collection as one object.'

        'The unary comma operator also works: , $list wraps it in a one-element array, and only that wrapper gets unrolled.'

    )

}