dissecting a Powershell string from a script

Greetings,

I received a script where the first two lines have me a bit befuddled. Can you help me break apart how it works?

function IsAlive ([string] $computer = $(throw "Computer name missing"))
#returns $true if snamed computer reachable. $false otherwise
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John DarbyPMAsked:
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footechConnect With a Mentor Commented:
Just a little more explanation on why it works like als315 described...
The function IsAlive accepts the parameter called $computer.  $computer is cast as a string type, and when the function is called $computer has a default value of $(throw "Computer name missing")).  The default value will be used when no other value has been given to it.
So if the function was called with
IsAlive
throw generates a terminating error.  But if the function was called with
IsAlive wkstn1
then $computer now equals the string "wkstn1" and the function continues.
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als315Connect With a Mentor Commented:
You can read about throw keyword here:
http://technet.microsoft.com/en-us/library/dd819510.aspx
In this case if computer name is missing, immediately will be returned error "Computer name missing"
Second line is comment (#)
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John DarbyPMAuthor Commented:
Thank you, both!
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