Different behaviors while passing parameters to PowerShell function

Question

I am trying to understand passing parameters to functions in PowerShell and it shows different behavior while passing single/multiple parameters.

can someone explain

Answer 1

You don't use brackets when sending input values to a function, so these two would be valid ways to send your inputs:

# only this adds two numbers correctly
$result1 = Add-Numbers 10 20
write-host "Result1: $result1"; 

#Passing single paramter works this way 
$result2 = SquareIt 15
write-host "Result2: $result2";

You send inputs to a function by either named parameters, or it just assumes which input to map to which input parameter by the order they are provided. You separate inputs with a space, per the examples above.

So for example you could also do:

Add-Numbers -Num1 10 -Num2 20
SquareIt -Num 15

You don't get an error when using the brackets because by doing so you've turned the input into an array, which then just gets sent to the first parameter. I.e, essentially you did this:

Add-Numbers -Num1 (10,20) -Num2 $null