increment a variable only when a conditional is true?

On Wed, Feb 19, 2020 at 10:33 AM thufir <hawat.thufir at gmail.com> wrote: > How do I decrement y? > > Pardon, output for a simpler example: > > <xy x="1" y="98"/> > <xy x="2" y="98"/> > <xy x="3" y="98"/> > <xy x="4" y="98"/> > <xy x="5" y="98"/> > <xy x="6" y="98"/> > <xy x="7" y="98"/> > <xy x="8" y="98"/> > <xy x="9" y="98"/> > > the FLWOR: > > xquery version "3.0"; > let $y := 99 > for $x in (1 to 9) > let $y := $y - 1 > return <xy x='{$x}' y='{$y}' /> > > > is it not possible to decrement $y without using some external scripting > function? That seems odd. > > > thanks, > > Thufir >

On 2020-02-19 7:57 a.m., Bridger Dyson-Smith wrote: > Hi Thufir - > > Maybe something like this will help? > > ``` > xquery version "3.1"; > > let $y := 99 > > for $x in (1 to 9) > count $iterator > let $decrease := $y - $iterator > return( > comment { "iterator = " || $iterator }, > comment { "decrease = " || $decrease }, > <xy x='{ $x }' y='{ $decrease }'/> > ) > ``` > > I'm basically ripping Walmsley's book off for this example -- see pages > ~135-7 (examples P-6,7). The `count` clause makes this work. > > Best, > Bridger > > PS Remember, the first step in avoiding a *trap* is knowing of its > existence. :) > > On Wed, Feb 19, 2020 at 10:33 AM thufir <hawat.thufir at gmail.com > <mailto:hawat.thufir at gmail.com>> wrote: > > How do I decrement y? > > Pardon, output for a simpler example: > > <xy x="1" y="98"/> > <xy x="2" y="98"/> > <xy x="3" y="98"/> > <xy x="4" y="98"/> > <xy x="5" y="98"/> > <xy x="6" y="98"/> > <xy x="7" y="98"/> > <xy x="8" y="98"/> > <xy x="9" y="98"/> > > the FLWOR: > > xquery version "3.0"; > let $y := 99 > for $x in (1 to 9) > let $y := $y - 1 > return <xy x='{$x}' y='{$y}' /> > > > is it not possible to decrement $y without using some external > scripting > function? That seems odd. > > > thanks, > > Thufir >

> On Feb 19, 2020, at 10:01 AM, thufir <hawat.thufir at gmail.com> wrote: > > where I'm trying to use attributes because I'm not sure how to conditionally nest tags. But, this is interesting. Not quite sure on syntax to set and then conditionally increment $x, however.

On 2020-02-19 1:05 p.m., Majewski, Steven Dennis (sdm7g) wrote: > > >> On Feb 19, 2020, at 10:01 AM, thufir <hawat.thufir at gmail.com >> <mailto:hawat.thufir at gmail.com>> wrote: >> >> where I'm trying to use attributes because I'm not sure how to >> conditionally nest tags. But, this is interesting. Not quite sure on >> syntax to set and then conditionally increment $x, however. > > Does “conditionally nest tags” mean that you want to make the > person[@numerical=“true”] elements children of the immediately previous > person[@numerical=“false”] elements ? > > If that is the case you can use “group by” > > > — Steve M. > >

> { for $I in $P return <number>{$I/@id, attribute x {$X[1]-1}, string($I)}</number> } </person>

> On Feb 19, 2020, at 8:28 PM, thufir <hawat.thufir at gmail.com> wrote: > > Hi Steve, > > yes, it certainly does. At this point, I'd settle for adding an attribute like "recordID", but that's exactly it. I'll take a closer look at "group by" a bit later, thanks for the pointer. See also: > > https://stackoverflow.com/q/60237739/262852 > > > thanks, > > Thufir > > On 2020-02-19 1:05 p.m., Majewski, Steven Dennis (sdm7g) wrote: >>> On Feb 19, 2020, at 10:01 AM, thufir <hawat.thufir at gmail.com <mailto:hawat.thufir at gmail.com>> wrote: >>> >>> where I'm trying to use attributes because I'm not sure how to conditionally nest tags. But, this is interesting. Not quite sure on syntax to set and then conditionally increment $x, however. >> Does “conditionally nest tags” mean that you want to make the person[@numerical=“true”] elements children of the immediately previous person[@numerical=“false”] elements ? >> If that is the case you can use “group by” >> — Steve M.

On 2020-02-19 6:55 p.m., Majewski, Steven Dennis (sdm7g) wrote: > The reason I asked was: although XQuery looks more procedural than XSLT, > it’s still basically a functional and declarative language, and thinking > about incrementing or decrementing variables is probably the wrong way > to think about solving your problem in XQuery. > Variables bind names to values over a particular scope, and they aren’t > updatable variables that you can increment or decrement. > > If what you want in English is roughly: > For person element where numerical = true , group by the > preceding-sibling where numerical = false > > That maps fairly simply into XQuery syntax: > > declare variable $XML := <xml> > <person id="1" x="0" numerical="false">people</person> > <person id="2" x="0" numerical="false">joe</person> > <person id="3" x="0" numerical="true">phone1</person> > <person id="4" x="0" numerical="true">phone2</person> > <person id="5" x="0" numerical="true">phone3</person> > <person id="6" x="0" numerical="false">sue</person> > <person id="7" x="0" numerical="true">cell4</person> > <person id="8" x="0" numerical="true">home5</person> > <person id="9" x="0" numerical="false">alice</person> > <person id="10" x="0" numerical="true">atrib6</person> > <person id="11" x="0" numerical="true">x7</person> > <person id="12" x="0" numerical="true">y9</person> > <person id="13" x="0" numerical="true">z10</person> > </xml> ; > > for $P in $XML/person > where $P[@numerical="true"] > let $PREV := $P/preceding-sibling::person[@numerical="false"][1] > group by $PREV > return <person name="{$PREV}" > { $P } </person> > > Yields: > > > <person name="joe"> > <person id="3" x="0" numerical="true">phone1</person> > <person id="4" x="0" numerical="true">phone2</person> > <person id="5" x="0" numerical="true">phone3</person> > </person> > <person name="sue"> > <person id="7" x="0" numerical="true">cell4</person> > <person id="8" x="0" numerical="true">home5</person> > </person> > <person name="alice"> > <person id="10" x="0" numerical="true">atrib6</person> > <person id="11" x="0" numerical="true">x7</person> > <person id="12" x="0" numerical="true">y9</person> > <person id="13" x="0" numerical="true">z10</person> > </person> > > Once the grouping is working, you can work on tweaking the output format > to exactly what you want. I tried to work towards something like what I > THOUGHT you might want. > I had a bit of trouble understanding that $PREV in the return expression > is an atomic string value and not a node, and that the other variables > in return expression are multiple valued ( thus the ‘[1]’s ), but I > ended up with this: > > > <people> { > for $P in $XML/person > where $P[@numerical="true"] > let $PREV := $P/preceding-sibling::person[@numerical="false"][1] > let $X := count($P[1]/preceding-sibling::person[@numerical="false"]) > group by $PREV > return <person name="{$PREV}" > x="{$X[1] - 1 }" > id="{$P[1]/preceding-sibling::person[@numerical="false"][1]/@id}" >> { for $I in $P return <number>{$I/@id, attribute x {$X[1]-1}, string($I)}</number> } </person> > } </people> > > Which yields: > > <people> > <person name="joe" x="1" id="2"> > <number id="3" x="1">phone1</number> > <number id="4" x="1">phone2</number> > <number id="5" x="1">phone3</number> > </person> > <person name="sue" x="2" id="6"> > <number id="7" x="2">cell4</number> > <number id="8" x="2">home5</number> > </person> > <person name="alice" x="3" id="9"> > <number id="10" x="3">atrib6</number> > <number id="11" x="3">x7</number> > <number id="12" x="3">y9</number> > <number id="13" x="3">z10</number> > </person> > </people> > > > Also more functional to think of use count or position expressions > instead of incrementing or decrementing variables. > > I’m hitting the Walmsley book myself now to try to understand those > issues with group by / return that were puzzling to me. > > > — Steve M. > > >> On Feb 19, 2020, at 8:28 PM, thufir <hawat.thufir at gmail.com >> <mailto:hawat.thufir at gmail.com>> wrote: >> >> Hi Steve, >> >> yes, it certainly does. At this point, I'd settle for adding an >> attribute like "recordID", but that's exactly it. I'll take a closer >> look at "group by" a bit later, thanks for the pointer. See also: >> >> https://stackoverflow.com/q/60237739/262852 >> >> >> thanks, >> >> Thufir >> >> On 2020-02-19 1:05 p.m., Majewski, Steven Dennis (sdm7g) wrote: >>>> On Feb 19, 2020, at 10:01 AM, thufir <hawat.thufir at gmail.com >>>> <mailto:hawat.thufir at gmail.com>> wrote: >>>> >>>> where I'm trying to use attributes because I'm not sure how to >>>> conditionally nest tags. But, this is interesting. Not quite sure >>>> on syntax to set and then conditionally increment $x, however. >>> Does “conditionally nest tags” mean that you want to make the >>> person[@numerical=“true”] elements children of the immediately >>> previous person[@numerical=“false”] elements ? >>> If that is the case you can use “group by” >>> — Steve M. >