Jagged PowerShell array is losing a dimension when only one element exists

Question

I have the following PowerShell function that works well for any input except for `1`. If I pass it an input of `1` it will return an array with two elements `1,1` instead of a single element which is itself an array of two elements `(1,1)`. Any ideas how I can make PowerShell return a jagged array with one element that is itself an array? ``` function getFactorPairs { param($n) $factorPairs = @() $maxDiv = [math]::sqrt($n) write-verbose "Max Divisor: $maxDiv" for($c = 1; $c -le $maxDiv; $c ++) { $o = $n / $c; if($o -eq [math]::floor($o)) { write-debug "Factor Pair: $c, $o" $factorPairs += ,@($c,$o) # comma tells powershell to add defined array as element in existing array instead of adding array elements to existing array } } return $factorPairs } ``` Here is my test and it's output showing the problem. You can see that the first example (1 as input) is returning a length of 2 even though there was only one factor pair found. The second example (6 as input) is working properly and is…

Accepted Answer

I tested this on the PowerShell V2 CTP on Windows XP, and saw the same results as the OP.

The problem appears to be PowerShell's habit of "flattening" collections as they're passed along the pipeline. A simple solution is to wrap the return value in an collection by prefacing the expression to be returned with the comma operator thus:

```
return ,$factorPairs
```

See Keith Hill's blog entry Effective PowerShell Item 8: Output Cardinality - Scalars, Collections and Empty Sets - Oh My! for a little more detail.

Hope this helps.

Jagged PowerShell array is losing a dimension when only one element exists

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