Powershell processing arrays in a multi dimensional array after defined number

Question

if i need to process all arrays in a multi dimensional array after skipping the first one how would i go about this?

in this case adding + 5 to each value. what if i want to start at the second array $mdarr[1]<

cls
$mdarr = @()
$i = @()
$ii = @()
$mdarr = @((0,1,2,3,4),(5,6,7,8,9),(10,11,12,13,14))

for ($i = 0; $i -lt $mdarr.Length; ++$i){
    for ($ii = 0; $ii -lt $mdarr[$i].Length; ++$i){
    $mdarr = $mdarr[$i][$ii] + 5
    }
}
write-host $mdarr

there is so much wrong with the above. the result i'm looking for should be:

((0,1,2,3,4),(10,11,12,13,14),(15,16,17,18,19))

how would this be done?

vonPryz · Accepted Answer · 2018-10-04 18:20:37Z

2

The problem is in updating the array contents. All that's needed is a nested loop to process elements in the inner arrays with appropriate indexing. Like so,

$mdarr = @((0,1,2,3,4),(5,6,7,8,9),(10,11,12,13,14))
for($i = 1; $i -lt $mdarr.Length; ++$i) {
    for($j = 0; $j -lt $mdarr[$i].Length; ++$j) {
        $mdarr[$i][$j] += 5
    }
}

$mdarr[1]
10
11
12
13
14

As why didn't the original work, let's analyze the code and see what was wrong:

# This starts from 1st element (index 0), which was to be skipped. Bug
for ($i = 0; $i -lt $mdarr.Length; ++$i){

    # Loop counters $ii and $i are confusing, name is almost same
    # What's more, $i is increased instead of $ii. Bug 
    for ($ii = 0; $ii -lt $mdarr[$i].Length; ++$i){
        # This doesn't make sense. It's overwriting the whole 
        # source array-of-arrays with a single value.
        # The array cell was to be updated instead. Bug
        $mdarr = $mdarr[$i][$ii] + 5
    }
}

To sum up, the idea was there. Due indexing bugs and inappropriate assignment operation, the outcome was wrong. Still, fixing is quite straightforward, as the main logic was okay.

edited Oct 4, 2018 at 18:20

answered Oct 4, 2018 at 18:11

vonPryz

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2 Comments

secondplace Over a year ago

i just ran into a situation where this would give me an error if the array contains only one value. Unable to index into an object of type System.Int32. what would need to be adjusted?

secondplace Over a year ago

turns out my input for the loop was flawed. i had to wrap the command in @() to return an array and not a scalar object.

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