Vista - Filter niggle

I must be doing something very basic wrong here but just can't see it.

I'm trying to create a simple filter to filter out odd numbered
values.

The code works when inside the script block of where-object.

PS Alias:\> 1,2,3,4,5,6 | where-object {$_ % 2 -eq 0}
2
4
6

I copied and pasted it to the Filter definition:

PS Alias:\> Filter OnlyEven {
>> $_ % 2 -eq 0
>> }
>>

And ran it as follows (when it didn't filter).

PS Alias:\> 1,2,3,4,5,6 | where-object {OnlyEven}
1
2
3
4
5
6

However, the Filter on its own does return True and False for the
appropriate values.

PS Alias:\> 1,2,3,4,5,6 | OnlyEven
False
True
False
True
False
True
PS Alias:\>

What very simple thing am I missing? Why aren't the objects discarded
by where-object when I use the Filter name inside the script block?

It's a niggle rather than a problem since I can just write any
necessary code in the script block and bypass filters altogether.

FWIW the example in about_filter.help.txt doesn't work for me either.

Waiting for someone to explain the "Doh!" moment to me.

Thanks

Andrew Watt MVP

You are basically returning everything in your filter
So make sure to return only even numbers using "if"

filter OnlyEven { if ($_ % 2 -eq 0) { $_ } }

[^_^]PS[131]+>1,2,3,4,5,6 | OnlyEven
2
4
6

"Andrew Watt [MVP]" wrote:

> And ran it as follows (when it didn't filter).
>
> PS Alias:\> 1,2,3,4,5,6 | where-object {OnlyEven}
> 1
> 2
> 3
> 4
> 5
> 6

The filter can't work inside a Where-Block like this, because the filter
always expects some input. Try this instead:

PS> 1,2,3,4,5,6 | where-object {$_|OnlyEven}
2
4
6

or if you like:

PS> 1,2,3,4,5,6 | where-object {$input|OnlyEven}
2
4
6

--
greetings
dreeschkind

If you want to use it with where-object, define OnlyEven as a function, not
a filter:

PS> function onlyEven {
>> $_ %2 -eq 0
>> }
>>
PS> 1..6 | where {onlyEven}
2
4
6

Jacques

"Andrew Watt [MVP]" <SVGDeveloper@aol.com> wrote in message
news:i5uel295kt0lbsoas2bc3d5iq1r44up4rk@4ax.com...
>I must be doing something very basic wrong here but just can't see it.
>
> I'm trying to create a simple filter to filter out odd numbered
> values.
>
> The code works when inside the script block of where-object.
>
> PS Alias:\> 1,2,3,4,5,6 | where-object {$_ % 2 -eq 0}
> 2
> 4
> 6
>
> I copied and pasted it to the Filter definition:
>
> PS Alias:\> Filter OnlyEven {
>>> $_ % 2 -eq 0
>>> }
>>>
>
> And ran it as follows (when it didn't filter).
>
> PS Alias:\> 1,2,3,4,5,6 | where-object {OnlyEven}
> 1
> 2
> 3
> 4
> 5
> 6
>
> However, the Filter on its own does return True and False for the
> appropriate values.
>
> PS Alias:\> 1,2,3,4,5,6 | OnlyEven
> False
> True
> False
> True
> False
> True
> PS Alias:\>
>
> What very simple thing am I missing? Why aren't the objects discarded
> by where-object when I use the Filter name inside the script block?
>
> It's a niggle rather than a problem since I can just write any
> necessary code in the script block and bypass filters altogether.
>
> FWIW the example in about_filter.help.txt doesn't work for me either.
>
> Waiting for someone to explain the "Doh!" moment to me.
>
> Thanks
>
> Andrew Watt MVP

Thanks.

Could you have someone fix the relevant part of About_Filter.help.txt?

Thanks

Andrew Watt MVP

On Sun, 12 Nov 2006 21:47:25 +0100, "Jacques Barathon [MS]"
<jbaratho@online.microsoft.com> wrote:

>If you want to use it with where-object, define OnlyEven as a function, not
>a filter:
>
>PS> function onlyEven {
>>> $_ %2 -eq 0
>>> }
>>>
>PS> 1..6 | where {onlyEven}
>2
>4
>6
>
>Jacques
>
>"Andrew Watt [MVP]" <SVGDeveloper@aol.com> wrote in message
>news:i5uel295kt0lbsoas2bc3d5iq1r44up4rk@4ax.com...
>>I must be doing something very basic wrong here but just can't see it.
>>
>> I'm trying to create a simple filter to filter out odd numbered
>> values.
>>
>> The code works when inside the script block of where-object.
>>
>> PS Alias:\> 1,2,3,4,5,6 | where-object {$_ % 2 -eq 0}
>> 2
>> 4
>> 6
>>
>> I copied and pasted it to the Filter definition:
>>
>> PS Alias:\> Filter OnlyEven {
>>>> $_ % 2 -eq 0
>>>> }
>>>>
>>
>> And ran it as follows (when it didn't filter).
>>
>> PS Alias:\> 1,2,3,4,5,6 | where-object {OnlyEven}
>> 1
>> 2
>> 3
>> 4
>> 5
>> 6
>>
>> However, the Filter on its own does return True and False for the
>> appropriate values.
>>
>> PS Alias:\> 1,2,3,4,5,6 | OnlyEven
>> False
>> True
>> False
>> True
>> False
>> True
>> PS Alias:\>
>>
>> What very simple thing am I missing? Why aren't the objects discarded
>> by where-object when I use the Filter name inside the script block?
>>
>> It's a niggle rather than a problem since I can just write any
>> necessary code in the script block and bypass filters altogether.
>>
>> FWIW the example in about_filter.help.txt doesn't work for me either.
>>
>> Waiting for someone to explain the "Doh!" moment to me.
>>
>> Thanks
>>
>> Andrew Watt MVP

On Sun, 12 Nov 2006 12:32:01 -0800, dreeschkind
<dreeschkind@discussions.microsoft.com> wrote:

>PS> 1,2,3,4,5,6 | where-object {$_|OnlyEven}

Thanks. That works.

Andrew Watt MVP

"Andrew Watt [MVP]" <SVGDeveloper@aol.com> wrote in message
news:gc2fl251278ql4fqbn08s0210k32oh62tt@4ax.com...
> Thanks.
>
> Could you have someone fix the relevant part of About_Filter.help.txt?
>
> Thanks
>
> Andrew Watt MVP

Please raise it on Connect.

Jacques