Vista Tutorial - What does the $() operator do?

I have googled and I've used get-help. I've even tried my own tests,
but I can't rell what the $() operator does.

I've seen it in people's code and I think I can tell, from the
context, what it does, but I'm mistaken.

#Example 1:
param(
[string] $wsdlLocation = $(throw "Please specify a WSDL
location"),
)

#Example 2
$s = indent "<$($reader.Name) "


I was feeling like I was finally nearing the crest of the learning
curve, to where I can actually use PowerShell instead of simply
running other people's scripts, then I run into this. :-)

Thanks!

--
Kevin Buchan
kevin.bucahn@xxxxxx[nospam]sanders.com

Kevin,

Sometimes you need to evaluate an expression and then use the results to do
something else.

Classicly you would probably do
$myvar = <some code that returns a value/object>
if ($mayvar -eq "<somevalue>") { do something else }

Using $() allows you to do this all in one line.
if($(<some code that returns a value/object>) -eq "<somevalue>") { do
something else }

You will see this a lot in code as people force an expression to be
evaluated, you may even see $($myvar) where $myvar is of a type that returns
an unhelpful object but placing that inside another $() actually takes you
to the value you want. I am sure smarter people can give more technical
answers.

James


"Kevin Buchan" <kevin.buchan@xxxxxx[Pls Don't Spam]sanders.com> wrote in
message newsmhoq3t1na8c4rg3gce6vgji0aoeiloqi2@xxxxxx

Hi Kevin,

Technically it is called a subexpression. It basically instructs PowerShell
to evaluate it first and use the result of the subexpression wherever the
subexpression was located. This is very useful when building strings using
properties of objects. For example, suppose you needed to include the
department of a user as part of a string, and that your user was in a
variable called $user. You would use subexpressions to do this as follows:

"Department: $($user.department)"

Without the subexpression syntax the .department suffix would be treated as
a literal part of the string.

--
Kirk Munro [MVP]
Poshoholic
http://www.poshoholic.com

"jas" <james.seatter@xxxxxx> wrote in message
news:CB52EE09-F062-4E6A-8EF9-EA663DF36A36@xxxxxx

>>> I am sure smarter people can give more technical answers.

Keith Hill is such a guy. I came across a very good explanation of
PowerShell parsing modes and as a sidebar the difference between several
types of expressions!

http://keithhill.spaces.live.com/blo...A97!6058.entry


What's the difference between grouping expressions (), subexpressions $()
and array subexpressions @()? A grouping expression can contain just a
single statement. A subexpression can contain multiple semicolon separated
statements. The output of each statement contributes to the output of the
subexpression. An array subexpression behaves just like a subexpression
except that it guarantees that the output will be an array. The two cases
where this makes a difference are 1) there is no output at all so the result
will be an empy array and 2) the result is a scalar value so the result will
be a single element array containg the scalar value. If the output is
already an array then the use of an array subexpession will have no affect
on the output i.e. array subexpressions do not wrap arrays inside of another
array.



"jas" <james.seatter@xxxxxx> wrote in message
news:CB52EE09-F062-4E6A-8EF9-EA663DF36A36@xxxxxx