implement indexer in loop

Hi guys !

loops in powershell is various and its awesome but it missing an indexer for example:

foreach($index,$item in $list) {
    "$index = $item"
}

is more elegant and short:

$index =  0
foreach($item in $list) {
    "$index = $item"
     $index++
}

[mklement0]

I like the idea; it complements @iRon7’s proposal to introduce an automatic $PSIndex variable in the pipeline: #13772

@doctordns, it’s helpful syntactic sugar; just a couple of use cases off the top of my head; I’m sure there are more.

^{Note: The original syntax was changed to reflect the later discussion; the index variable now comes after the iteration expression, separate with ;}

# Parellel array processing
$a = 'foo', 'bar'
$b = 'baz', 'qux'
$c = 'and' 'so on'
foreach ($aElem in $a; $i) { # WISHFUL THINKING
  $bElem, $cElem = $b[$i], $c[$i]
  # ...
}

# Get only every 2nd element
$a = 'foo', 'bar', 'baz', 'quux'
foreach ($aElem in $a; $i) { # WISHFUL THINKING
  if ($i % 2) { continue }
}

As a largely moot aside: Quite some time ago, in #3830, I had proposed allowing syntax such as foreach ($a) { ... } - not having to specify an iteration variable explicitly and defaulting to $_ / $PSItem; the proposal was rejected, but it would have allowed us a unified approach with respect to an automatic $PSIndex as well.

[Jaykul]

I have to say that whenever I’ve needed something like this, I’ve just changed to a for(){} loop, or added a counter variable.

I don’t mind the idea of adding syntax to foreach(){} to define a counter variable to be incremented for me, but I’m not convinced the savings are worth it. I mean, is this:

foreach($item in @($List); $index) {           
  $item | add-member Index $index -PassThru    
}                                              

Really better than this:

$index=0; foreach($item in @($List)) {         
  $item | add-member Index ($index++) -PassThru
}

Remember that it’s not just about saving you a few keystrokes, it’s also about clarity and readability …

To make it clearer, we could add a parameter (there’s precedent in switch):

foreach($item in @($List)) -counter index {           
  $item | add-member Index $index -PassThru    
}