Maybe my thinking of them as arrays is where my lack of understanding comes 
from.
when you say /root/peter[3]
is that basically setting position() (within the current context) equal to 3 
?
when wecome out position goes back to its original value - e.g. if we were 
in another for-each or a template?

and thus that would seem to explain why /root/peter[position()-1] ?



"Jason Burr" <JasonBurr@d...> wrote in message 
news:C09DB026-A18E-49D5-9286-13AA9A93593B@m......
> Ok this has gone way further than I ever wanted. I did get the answer to 
> the
> problem so thanks alot on that Marrow.
>
> I guess though now my curiosity is getting the best of me and that I am a
> bit lost on this point so here goes.
>
> Regarding Neils post.
>
> I agree though you could do
>
> test1(test2())
> or
> function test1() {
>  return test1 = test2()
> }
> which would be the same thing the confusion is that this is acceptable
> [position()=last()-1]
> which I read as assigning an argument from a function to another function
> similar to example one above. matter of how an argument/parameter is 
> assigned
> in a given language. Anyway.....
>
> Marrow
>
> I guess based on what you said I am confused if I am in the same nodal
> context why that doesn't work if
> [position()=last()-1] works
> or
> [postion()=4] works
> or the solution you gave works
> variable prev-position=postion()-1
> [postion()=$prev-position]
>
> I think that if I get you right (hopefully) that what you are saying is 
> that
> inside of the predicate I am outside the current context???? If that is so
> then why does last()-1 work is that because it retains current()?
>
> "Jason Burr" wrote:
>
>> I think what he was trying to say is this (if I'm wrong I hope he will
>> correct me)
>>
>> postion() can be assigned or it can be evaluated but it can't do both at 
>> the
>> same time.
>>
>> In other words
>>
>> 1. You can ask position() what it's value is
>> 2. You can tell position() what it's value is
>> 3. You can't ask it what it is and then tell it what it is at the same 
>> time.
>>
>> By assigning a variable you are asking it first and then telling it later
>> what it should be.
>>
>> The reason this seemed a wee bit nonsensical to me is that generally when
>> programming you have the ability to assign a value from the same value.
>> Because generally the statement to the right of a value assignment is
>> evaluated prior to its assignment on the left.
>>
>> so in programming generally this is a perfectly acceptable thing to do:
>> x = x + 1
>> or
>> myObjectValue = myObjectValue - 1
>> because its being read more like
>>
>> n = (x + 1)
>> x = n
>>
>> whereas with the predicate statement it is being read literally as
>> x = x + 1
>> which can never be evaluated
>>
>> I think that is is because it is opening position() to accept a value and
>> therefore it has no value when requested after being opened for input. 
>> I'm
>> sure this is somehow by design and a perfectly good reason for it exists.
>> (late bound early bound language?)
>>
>>
>> "johndoe@d..." wrote:
>>
>> >     I have seen and used the <xsl:variable name="PrevPos"
>> > select="position() - 1" /> through trial and error, but I have not 
>> > really
>> > understood why exactly this is. I read the explanation provided by 
>> > Marrow
>> > but it seems to have gone over my head.
>> >
>> >
>> >
>> > "Jason Burr" <JasonBurr@d...> wrote in message
>> > news:DD97D787-424F-4D74-B742-C69F5084D333@m......
>> > > Marrow,
>> > >
>> > > Thanks simply assigning  variable worked (never tried that because of 
>> > > all
>> > > the "no variable reassignment" griping)
>> > >
>> > > My thinking on the predicate was that the order of execution would be
>> > >
>> > > 1. evaluate value of the (current) position()-1
>> > > 2. assign that value to position()
>> > > 3. retrive the node given the assigned position
>> > >
>> > > I guess my thinking was that = doesn't evaluate the truth a statement 
>> > > such
>> > > as
>> > >
>> > > x = x + 1
>> > >
>> > > But rather
>> > >
>> > > (newvalue of x <--- (x - 1))
>> > >
>> > > Anyway good stuff to know thanks again.
>> > >
>> > > "Marrow" wrote:
>> > >
>> > >> Hi Jason,
>> > >>
>> > >> > Not trying to accomplish any thing was just messing around and 
>> > >> > thought
>> > >> that
>> > >> > it might be a good way to check for the last record in a group 
>> > >> > during a
>> > >> loop.
>> > >> > Since I can't reassign variables and position() tells me where in 
>> > >> > a
>> > >> > loop I
>> > >> am
>> > >> > and position() can also be used to specify a node to look up it 
>> > >> > seemed
>> > >> (maybe
>> > >> > foolishly) that this was an easy way to know if the current node 
>> > >> > and
>> > >> previous
>> > >> > node for a given value match.
>> > >>
>> > >> The position() function when used **outside** a predicate will give 
>> > >> you
>> > >> the
>> > >> position within the currently processed node-set (e.g. that selected 
>> > >> by a
>> > >> @select on <xsl:apply-templates> or <xsl:for-each>).  When the 
>> > >> position()
>> > >> function is used **within** a predicate then it ruturns the index of 
>> > >> the
>> > >> node within the nodes selected by the XPath expression to the left 
>> > >> of the
>> > >> predicate.
>> > >>
>> > >> Your problem remains...
>> > >>
>> > >> >   <xsl:when test="/foo/bar[position()=position()-1]/@attrib">
>> > >>
>> > >> read the bit inside the [] predicate! ;)
>> > >>
>> > >> How can "position()=position()-1" ever evaluate to true???  It 
>> > >> can't... x
>> > >> can never equal (x - 1)... complete impossibility!  ;)
>> > >>
>> > >> Maybe one of those position()'s is the position prior to the 
>> > >> predicate?
>> > >> In
>> > >> which case you would need to store one to a variable first, e.g 
>> > >> something
>> > >> like...
>> > >>
>> > >>  <xsl:for-each select="bar">
>> > >>    <xsl:variable name="curr-posn" select="position()"/>
>> > >>    <xsl:choose>
>> > >>    <xsl:when test="/foo/bar[position()=$curr-posn -1]/@attrib">
>> > >>       ...
>> > >>
>> > >> or even just calc the index, e.g.
>> > >>
>> > >>  <xsl:for-each select="bar">
>> > >>    <xsl:variable name="prev-posn" select="position() - 1"/>
>> > >>    <xsl:choose>
>> > >>    <xsl:when test="/foo/bar[$prev-posn]/@attrib">
>> > >>       ...
>> > >>
>> > >> Cheers
>> > >> Marrow
>> > >>
>> > >> "Jason Burr" <JasonBurr@d...> wrote in message
>> > >> news:C68421B0-71EE-4519-B453-EEB0735C5504@m......
>> > >> > Hey Marrow,
>> > >> >
>> > >> > Not trying to accomplish any thing was just messing around and 
>> > >> > thought
>> > >> that
>> > >> > it might be a good way to check for the last record in a group 
>> > >> > during a
>> > >> loop.
>> > >> > Since I can't reassign variables and position() tells me where in 
>> > >> > a
>> > >> > loop I
>> > >> am
>> > >> > and position() can also be used to specify a node to look up it 
>> > >> > seemed
>> > >> (maybe
>> > >> > foolishly) that this was an easy way to know if the current node 
>> > >> > and
>> > >> previous
>> > >> > node for a given value match. I am aware of Muenchian (you may 
>> > >> > have
>> > >> > helped
>> > >> me
>> > >> > out with that).
>> > >> >
>> > >> > Anyway the context of that example would have been in
>> > >> >
>> > >> > <foo>
>> > >> >   <bar attrib='test'>
>> > >> >   <bar attrib='test'>
>> > >> >   <bar attrib='test2'>
>> > >> > </foo>
>> > >> >
>> > >> > <xsl:for-each select="bar">
>> > >> >   <xsl:choose>
>> > >> >   <xsl:when test="/foo/bar[position()=position()-1]/@attrib">
>> > >> >    <xsl:value-of select="@attrib"/>
>> > >> >   </xsl:when>
>> > >> >   <xsl:otherwise>
>> > >> >     <xsl:value-of select="@attrib"/> end of group
>> > >> >   </xsl:otherwise>
>> > >> >   </xsl:choose>
>> > >> > </xsl:for-each>
>> > >> >
>> > >> > Result expected
>> > >> >
>> > >> > test
>> > >> > test end of group
>> > >> > test2
>> > >> >
>> > >> > Clearly I didn't mess with the keys or anything for grouping but 
>> > >> > this
>> > >> would
>> > >> > work if the xml was ordered or if using the Muenchian Technique. 
>> > >> > (that
>> > >> > is
>> > >> if
>> > >> > it evaluated like it does when using value-of)
>> > >> >
>> > >> > As far as it evaluating to nothing thats not completely true 
>> > >> > becuase if
>> > >> > I
>> > >> > hard code in the value of the position
>> > >> >
>> > >> > <xsl:value-of select="/foo/bar[position()=3]/@attrib"/>
>> > >> >
>> > >> > The the result would be
>> > >> >
>> > >> > test2
>> > >> >
>> > >> > and if I do
>> > >> >
>> > >> > <xsl:value-of select="position()-1"/>
>> > >> >
>> > >> > I would get
>> > >> >
>> > >> > 0
>> > >> > 1
>> > >> > 2
>> > >> >
>> > >> > So my general question was why would that not evaluate to the 
>> > >> > value of
>> > >> > the
>> > >> > node (which does exist) and return the value requested. Further if
>> > >> > there
>> > >> is
>> > >> > no way for this to work then is there another way to evaluate the 
>> > >> > same
>> > >> thing
>> > >> > (the previous node processed in a for-each)
>> > >> >
>> > >> > Thanks,
>> > >> >
>> > >> > Jason
>> > >> >
>> > >> >
>> > >> >
>> > >> > "Marrow" wrote:
>> > >> >
>> > >> > > Hi Jason,
>> > >> > >
>> > >> > > > But that this never returns a result
>> > >> > > >
>> > >> > > > <xsl:value-of 
>> > >> > > > select="/foo/bar[position()=position()-1]/@attrib"/>
>> > >> > >
>> > >> > > Of course it won't ever return anything...  the predicate []
>> > >> > > expression
>> > >> can
>> > >> > > never evalaute to true.
>> > >> > >
>> > >> > > > What I want to do here is look at the last record in a loop to 
>> > >> > > > see
>> > >> > > > if
>> > >> I am
>> > >> > > > at the end of a grouping (begininig of the next actually)
>> > >> > >
>> > >> > > Based on what you have described so far (but not seeing more of 
>> > >> > > the
>> > >> > > XSLT
>> > >> and
>> > >> > > XML) I'd say it'is unlikely that your current method of doing
>> > >> > > grouping
>> > >> will
>> > >> > > work.  There are a couple of ways of doing grouping in XSLT 
>> > >> > > 1.0 - the
>> > >> > > Muenchian Technique and preceding-sibling technique.  I'm sure 
>> > >> > > if you
>> > >> post
>> > >> > > an example of what your are trying to do someone will be able to 
>> > >> > > show
>> > >> you
>> > >> > > how to do these.
>> > >> > >
>> > >> > > Cheers
>> > >> > > Marrow
>> > >> > > http://www.marrowsoft.com - home of Xselerator (XSLT IDE and
>> > >> > > debugger)
>> > >> > > http://www.topxml.com/Xselerator
>> > >> > >
>> > >> > >
>> > >> > > "Jason Burr" <JasonBurr@d...> wrote in 
>> > >> > > message
>> > >> > > news:3CEE074F-AD95-4124-ADD2-8DB46106D9BA@m......
>> > >> > > > Can someone explain why doing this writes a number one less 
>> > >> > > > than
>> > >> > > > the
>> > >> > > current
>> > >> > > > position.
>> > >> > > >
>> > >> > > > <xsl:value-of select="position()-1"/>
>> > >> > > >
>> > >> > > > Doing this will display a specific positions value
>> > >> > > >
>> > >> > > > <xsl:value-of select="/foo/bar[position()=3]/@attrib"/>
>> > >> > > >
>> > >> > > > But that this never returns a result
>> > >> > > >
>> > >> > > > <xsl:value-of 
>> > >> > > > select="/foo/bar[position()=position()-1]/@attrib"/>
>> > >> > > >
>> > >> > > > What I want to do here is look at the last record in a loop to 
>> > >> > > > see
>> > >> > > > if
>> > >> I am
>> > >> > > > at the end of a grouping (begininig of the next actually)
>> > >> > > >
>> > >> > >
>> > >> > >
>> > >> > >
>> > >>
>> > >>
>> > >>
>> >
>> >
>> >