Switch statement not matching all conditions

user_13232155 0
Viewed 66

I must be missing something here. I'm counting up a list, and want to skip over specific numbers, so I made a switch statement:

$locationNumber = 00
DO {
    $locationNumber++
    switch ($locationNumber) {
    21 {$locationNumber++}
    31 {$locationNumber++}
    43 {$locationNumber++}
    44 {$locationNumber++}
    49 {$locationNumber++}
    51 {$locationNumber++}
    }
    Write-Host $locationNumber
} while ($locationNumber -lt 53)

Here's the output:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 22 23 24 25 26 27 28 29 30 32 33 34 35 36 37 38 39 40 41 42 44 45 46 47 48 50 52 53

Notice that 44 shows up, even though I have no breaks. Can someone tell me why/a way around this?

Thanks,

EDIT: Added more code for context

switch-statement powershell
3 Answers

What you probably want is the switches default clause.

If you move the Write-Host to default in the switch statement, this means that if the other conditions are not met, then default to this action.

$locationNumber = 00
DO {
    $locationNumber++
    switch ($locationNumber) {
    21 {}
    31 {}
    43 {}
    44 {}
    49 {}
    51 {}
    default {Write-Host $locationNumber}
    }
} while ($locationNumber -lt 53)
user_39614720

If you want to eliminate a fixed set of numbers - 21, 31, 43, 44, 49, 51 - from a series of numbers - 1 through 53:

$(
  switch (1..53) {
    { $_ -notin 21, 31, 43, 44, 49, 51 } { $_ }
  }
) -join ' '

The above yields (line-wrapped for readability) - note how all the numbers in the list above are missing:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 22 23 24 25 26 27 28 29
 30 32 33 34 35 36 37 38 39 40 41 42 45 46 47 48 50 52 53

To capture the numbers in an array, simply assign to a variable in lieu of the $(...):
$nums = switch { ... }

The above takes advantage of the following features:

  • .., the range operator, to create a series of integers as an array.

  • the switch statement accepting script blocks ({ ... }) as branch conditionals, in which the input object at hand, $_ can be tested via arbitrary expressions.

  • the -notin operator, which tests a scalar LHS for not being contained in a RHS collection.

As for what you tried:

By applying ++ to the numbers you wanted to skip, they were nonetheless printed by the Write-Host statement executed in the same iteration of the do statement, after the switch statement.

Andrew Ryan Davis' helpful answer shows a solution to that problem via the default branch. While the solution above is much more concise, Andrew's answer is actually faster, though that will likely not matter in practice.

user_453750

Appreciate the help, but I just ended up doing

$locationNumber = 00
DO {
    $locationNumber++
    switch ($locationNumber) {
    21 {$locationNumber++}
    31 {$locationNumber++}
    43 {$locationNumber += 3}
    47 {$locationNumber++}
    49 {$locationNumber++}
    51 {$locationNumber++}
    }

    Write-Host $locationNumber
    
} while ($locationNumber -lt 53)

Where I added 3 to 43 to skip the ones I didn't need. Thanks.

user_132321550
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