re: Find the Index Number of a Value in a PowerShell Array

JV — Thu, 22 Dec 2011 00:11:46 GMT

Exactly the same way. You didn't read the article very closely.

PS>$x='helo','world','in','space','bees','knees'

PS>[array]::IndexOf($x,'space')

re: Find the Index Number of a Value in a PowerShell Array

jlo — Wed, 21 Dec 2011 17:33:24 GMT

Any thoughts on how to make it find an index if the array is not a list of numbers?

re: Find the Index Number of a Value in a PowerShell Array

Jlo — Tue, 13 Dec 2011 12:07:28 GMT

Could you give a quick example of getting an index number if the array is not a set of numbers? The common example would be getting an array from a text list of pc names.

Thank you for the article.

re: Find the Index Number of a Value in a PowerShell Array

Klaus Schulte — Wed, 07 Dec 2011 10:03:24 GMT

Hi Ed,

indexing into an array and finding the index of an array element are quite a common task that have been well explained here!

But ... As usual :-) ...I have some small comments to add here ...

The statement [array]::indexof($array,39) works correctly if there is at most one occurrence of the element in question. If there are more than one elements having the same value in the array ... indexof will retrieve the index of the first matching element. There are overloads of "IndexOf" available that will require to add a startindex ( and an index range) to find the next or simply another occurrence of the value we wnat to find. ( "LastIndexOf" returns the index of the last occurrence :-)

To conclude: If the value is not present, -1 is returned.

Another ... more or less ... "pholosophical" issue is buried in the line

$array[[int]($array.GetUpperBound(0)/2)..($array.GetUpperBound(0))]

I thought it is hard to read and added an additional variable "$high=$array.GetUpperBound(0)"

which results in

$array[[int]($high/2)..$high]

and I asked myselt if this is only "nice" or if it is more than that?

Actually I wanted to measure the performance and if you are using this statement inside a loop I tried to find out, if it is running faster!

So I did the following

PS C:\Users\Schulte> $array=1..10000

PS C:\Users\Schulte> Measure-Command {for ($i=0; $i -lt 100; $i++) { for ($j=[int]($array.GetUpperBound(0)/2); $j -le ($array.GetUpperBound(0)); $j++) {} }}

Days : 0

Hours : 0

Minutes : 0

Seconds : 1

Milliseconds : 790

Ticks : 17903169

TotalDays : 2,07212604166667E-05

TotalHours : 0,00049731025

TotalMinutes : 0,029838615

TotalSeconds : 1,7903169

TotalMilliseconds : 1790,3169

PS C:\Users\Schulte> $high=$array.GetUpperBound(0)

PS C:\Users\Schulte> $high

9999

Now the other approach

PS C:\Users\Schulte> Measure-command {for ($i=0; $i -lt 100; $i++) { for ($j=[int]($high/2); $j -le $high; $j++){} }}

Days : 0

Hours : 0

Minutes : 0

Seconds : 0

Milliseconds : 733

Ticks : 7331893

TotalDays : 8,48598726851852E-06

TotalHours : 0,000203663694444444

TotalMinutes : 0,0122198216666667

TotalSeconds : 0,7331893

TotalMilliseconds : 733,1893

So it looks like "$array.GetUpperBound(0)" is permanently reevaluated inside the loop which might cause an issue!

Klaus