From: Michael Kay <mike@sa...>  20130206 23:08:37

On further investigation the tail call seems to be a red herring. In the inner inline function $second, the closure contains two variables $countfun and $x, and the slot numbers for these variable references have not been allocated (properly or at all) so values are being picked up from the wrong place. To be continued... Michael Kay Saxonica On 06/02/2013 22:32, Michael Kay wrote: > > I have added this to the XSLT 3.0 test suite as test case > higherorderfunctions068, and I confirm it is still failing with the > current development build. > > The hypothesis I am exploring is that it is an interaction between > function closures and tail recursion; my suspicion is that when the > stackframe is reused/overwritten for the purpose of tailrecursion, > the values required for the function closure are being corrupted. It's > all pretty complex! > > Michael Kay > Saxonica > > On 06/02/2013 03:14, Abel Braaksma wrote: >> When I define the following continuation version of the Fibonacci >> sequencein XSLT 3: >> >> <xsl:function name="f:fib"> >> <xsl:param name="n" as="xs:integer" /> >> <xsl:param name="countfun" as="function(*)" /> >> >> <xsl:sequence select=" >> if ($n = 1 or $n = 2) >> then $countfun(1) >> else let $first := >> function($x as xs:integer) as function(*) >> { >> let $second := function($y as xs:integer) as >> function(*) >> { >> $countfun($x + $y) >> } >> return f:fib($n  2, $second) >> } >> return f:fib($n  1, $first)" /> >> </xsl:function> >> >> and I call it as follows: >> >> <xsl:valueof select="f:fib(10, function($a as xs:integer){$a})" /> >> >> the expected result is 55. However, I receive the following error: >> >> Engine name: SaxonEE 9.4.0.4 >> Severity: fatal >> Description: Required item type of second argument of anonymous >> function is function(); supplied value has item type xs:integer >> Start location: 36:0 >> URL: http://www.w3.org/TR/xslt20/#errXTTE0790 >> >> The function is inspired by this snippet http://fssnip.net/eU, though >> other functional languages have similar examples. The idea behind the >> excercise is to eliminate the double recursive exit pointof the >> function by creating a continuation function. However, either the >> error is confusing(I don't see any anonymous function call with >> afunction argument) or something else is happening. >> >> I also tried the fully typed version, and an untyped version. Here's >> the fully typed variant: >> >> <xsl:function name="f:fib" as="xs:integer"> >> <xsl:param name="n" as="xs:integer" /> >> <xsl:param name="countfun" as="function(xs:integer) as xs:integer" /> >> >> <xsl:sequence select=" >> if ($n = 1 or $n = 2) >> then $countfun(1) >> else let $first := >> function($x as xs:integer) as xs:integer >> { >> let $second := function($y as xs:integer) as >> xs:integer >> { >> $countfun($x + $y) >> } >> return f:fib($n  2, $second) >> } >> return f:fib($n  1, $first)" /> >> </xsl:function> >> >> >> Any idea what I'm missing here, or is this perhaps an error with Saxon? >> >> Thanks, >> Abel >> >> >> >> >>  >> Free NextGen Firewall Hardware Offer >> Buy your Sophos nextgen firewall before the end March 2013 >> and get the hardware for free! Learn more. >> http://p.sf.net/sfu/sophosd2dfeb >> >> >> _______________________________________________ >> saxonhelp mailing list archived athttp://saxon.markmail.org/ >> saxonhelp@... >> https://lists.sourceforge.net/lists/listinfo/saxonhelp > > > >  > Free NextGen Firewall Hardware Offer > Buy your Sophos nextgen firewall before the end March 2013 > and get the hardware for free! Learn more. > http://p.sf.net/sfu/sophosd2dfeb > > > _______________________________________________ > saxonhelp mailing list archived at http://saxon.markmail.org/ > saxonhelp@... > https://lists.sourceforge.net/lists/listinfo/saxonhelp 