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conditionals.md

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Conditionals

Introduction

When you write code, you often have to handle different scenarios, that's where conditional statements come in.

Operators

An important part of creating conditional statements is using comparison operators. They could be an entire lesson on their own, but thankfully the PowerShell documentation has great documentation on them, so I recommend you have a look.

If

If is the basic conditional statement. Basically, if a condition is met, execute the statement in the brackets. THe syntax is as follows:

if (<Condition>){
    # Code to execute
}

Here's an example:

$RandomNumber = Get-Random -Minimum 1 -Maximum 3 # Get a random number, either 1 or 2
if ($RandomNumber -eq 2){
    Write-Host "I got a 2!"
}
if ($RandomNumber -eq 1){
    Write-Host "I got a 1!"
}

Feel free to run the above code yourself :). The above code shows a problem with using just if. Thankfully this problem has been solved with else

If/Else

The else statement solves the problem where you want something like this: If condition X is met do this, otherwise do that.

If (<condition>)
{
    # Run code if condition is met
} else {
    # Run code if condition is not met
}

Our previous example can now become:

$RandomNumber = Get-Random -Minimum 1 -Maximum 3 # Get a random number, either 1 or 2
if ($RandomNumber -eq 2){
    Write-Host "I got a 2!"
} else {
    Write-Host "I got a 1!"
}

Now that's great, but what if I want to handle more cases?

If/Elseif/Else

If you want to handle more than two cases, you can do the following:

if (<condition1>)
{

} elseif (<condtion2>)
{

} elseif (<condtion3>)
{
    
} else
{

}

The way the elseif configuration works is the following:

  1. Is the condition in if met? If so, execute the code in the if block and skip the rest, otherwise go to the next section.

  2. If the condition in if is not met, evaluate elseif, if that condition is met run the code in the elseif and ignore the rest. Otherwise go to the next section.

  3. If the condition in elseif is not met, evaluate the next elseif, if that condition is met run the code in the elseif and ignore the rest. Otherwise go to the next section.

  4. If none of the sections evaluate to $true run the code in the else block.

What this means is that you need to make sure to properly order and prioritize your blocks.

Here's a concrete example:

I have a 10-sided dice, I can roll it 10 times and then I get a score based on the following rules:

  1. If I roll a 2, I get 10 points
  2. If I roll an even number I get 5 points
  3. If I roll a 3 I get 3 points
  4. Everything else I get 1 point

The following are my rolls: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

❕ Run through each rule manually first.

Here are all our conditional statements:

$roll -eq 2
[int]($roll/2) -eq $roll/2
$roll -eq 3

Here are a different configurations:

$rolls = 1..10
$total = 0
foreach ($roll in $rolls)
{
    if ($roll -eq 3){
        $total += 3
    } elseif ([int]($roll/2) -eq $roll/2) {
        $total += 5
    } elseif ($roll -eq 2){
        $total+=10
    }else {
        $total+=1
    }
}
$total
# Result
# 32

Another one:

$rolls = 1..10
$total = 0
foreach ($roll in $rolls)
{
    if ([int]($roll/2) -eq $roll/2){
        $total += 5
    } elseif ($roll -eq 3) {
        $total += 3
    } elseif ($roll -eq 2){
        $total+=10
    }else {
        $total+=1
    }
}
$total
# Result
# 32

and finally:

$rolls = 1..10
$total = 0
foreach ($roll in $rolls)
{
    if ($roll -eq 2){
        $total += 10
    } elseif ($roll -eq 3) {
        $total += 3
    } elseif ([int]($roll/2) -eq $roll/2){
        $total+=5
    }else {
        $total+=1
    }
}
$total
# Result
# 37

As you can see, the order matters!

Switch

Now if we look at the last example, what if every single roll had its own specific number of points? You would have to write and if/elseif/else satement for every single case, which can become very annoying. Thankfully switch is here!

Let's say those are my rules:

Roll 1 = 10 points Roll 2 = 10 points Roll 3 = 1 points Roll 4 = 5 points Roll 5 = 9 points Roll 6 = 6 points Roll 7 = 4 points Roll 8 = 8 points Roll 9 = 9 points Roll 10 = 2 points

With a switch we can do the following:

$rolls = 1..10
$total = 0
foreach ($roll in $rolls)
{
    switch ($roll)
    {
        1 {$total+=10}
        2 {$total+=10}
        3 {$total+=1}
        4 {$total+=5}
        5 {$total+=9}
        6 {$total+=6}
        7 {$total+=4}
        8 {$total+=8}
        9 {$total+=9}
        10 {$total+=2}
    }
}
$total
# Result:
# 64