我无法理解为什么 XSLT(Saxon 9.1 和 9.5)在使用包含已排序序列的变量时的工作方式。

这是我的程序的输出，其中嵌入了我的三个问题:

<?xml version="1.0" encoding="UTF-8"?>
The following sequence is unsorted...

  sequence $list                        = (<contribution e="4"/><contribution e="1"/><contribution e="2"/><contribution e="8"/>)

It is, as I expected, in document order.

The following sequence is explicitly sorted...

  sequence $sorted-list                 = (<contribution e="8"/><contribution e="4"/><contribution e="2"/><contribution e="1"/>)

It is, as I expected, sorted in descending numerical @e order.

In the following output, I expect for the @e values from $list to be in document order,
and for the @e values from $sorted-list to be in descending numerical order...

  value-of $list/@e                     = (4 1 2 8)
  value-of $sorted-list/@e              = (4 1 2 8)

But both are in document order.

Specifically, the $sorted-list/@e values are NOT listed in descending numerical @e order.
(Question 1: ...By the way, why can't I use 'xsl:sequence select="$list/@e"' here?)

Next, here's the real work that I'm interested in. It is a function that computes a running
subtotal of the elements passed in. Order is critical here. I expect for my sorted list to provide
@e values to the function in the order that I explicitly put them in the definition of $sorted-list.
So, in the following call, I send in the sequence that I think SHOULD have been sorted...

  sequence f($sorted-list/@e)           = (0 4 5 7 15)

But my result set is a list of running subtotals that are obviously not correctly ordered.
Question 2: Is this a bug, or evidence of a gap in my comprehension?

In the following call, I send a sequence that's explicitly ordered...

  sequence f(for...$sorted-list[$i]/@e) = (0 8 12 14 15)

...and I receive the sequence I need. I can use this as a workaround.

Question 3: Why is it that I must explicitly [re-]sort the $sorted-list sequence as I pass it to util:f()?

这是我的输入 XML:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <contribution e="4"/>
    <contribution e="1"/>
    <contribution e="2"/>
    <contribution e="8"/>
</root>

...还有我的 XSLT:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:util="http://www.method-r.com/util"
    exclude-result-prefixes="xs util"
    version="2.0">

    <xsl:template match="/">
The following sequence is unsorted...

  sequence $list                        = (<xsl:sequence select="$list"/>)

It is, as I expected, in document order.

The following sequence is explicitly sorted...

  sequence $sorted-list                 = (<xsl:sequence select="$sorted-list"/>)

It is, as I expected, sorted in descending numerical @e order.

In the following output, I expect for the @e values from $list to be in document order,
and for the @e values from $sorted-list to be in descending numerical order...

  value-of $list/@e                     = (<xsl:value-of select="$list/@e"/>)
  value-of $sorted-list/@e              = (<xsl:value-of select="$sorted-list/@e"/>)

But both are in document order.

Specifically, the $sorted-list/@e values are NOT listed in descending numerical @e order.
(Question 1: ...By the way, why can't I use 'xsl:sequence select="$list/@e"' here?)

Next, here's the real work that I'm interested in. It is a function that computes a running
subtotal of the elements passed in. Order is critical here. I expect for my sorted list to provide
@e values to the function in the order that I explicitly put them in the definition of $sorted-list.
So, in the following call, I send in the sequence that I think SHOULD have been sorted...

  sequence f($sorted-list/@e)           = (<xsl:sequence select="util:f(0, $sorted-list/@e)"/>)

But my result set is a list of running subtotals that are obviously not correctly ordered.
Question 2: Is this a bug, or evidence of a gap in my comprehension?

In the following call, I send a sequence that's explicitly ordered...

  sequence f(for...$sorted-list[$i]/@e) = (<xsl:sequence select="util:f(0, for $i in 1 to count($sorted-list) return $sorted-list[$i]/@e)"/>)

...and I receive the sequence I need. I can use this as a workaround.

Question 3: Why is it that I must explicitly [re-]sort the $sorted-list sequence as I pass it to util:f()?

<xsl:text/>
    </xsl:template>



    <xsl:variable name="list" as="element()*" select="//contribution"/>

    <xsl:variable name="sorted-list" as="element()*">
        <xsl:perform-sort select="$list">
            <xsl:sort select="number(@e)" order="descending"/>
        </xsl:perform-sort>
    </xsl:variable>



    <xsl:function name="util:f" as="xs:double*">
        <xsl:param name="sum0" as="xs:double"/>
        <xsl:param name="list" as="xs:double*"/>
        <xsl:sequence select="util:cumulative-list-2((), $list)"/>
    </xsl:function>

    <xsl:function name="util:cumulative-list-2" as="xs:double*">
        <xsl:param name="list" as="xs:double*"/>
        <xsl:param name="list-remainder" as="xs:double*"/>
        <xsl:choose>
            <xsl:when test="not(exists($list-remainder))">
                <xsl:sequence select="$list"/>
            </xsl:when>
            <xsl:otherwise>
                <xsl:sequence select="util:cumulative-list-2(
                    if (empty($list)) then
                    (0, $list-remainder[1])
                    else 
                    ($list, $list[last()] + $list-remainder[1]),
                    remove($list-remainder, 1)
                    )"/>
            </xsl:otherwise>
        </xsl:choose>
    </xsl:function> 


</xsl:stylesheet>

最佳答案

通过执行 $sorted-list/@e 的步骤，/@e 将选择所有 @e 属性并按文档顺序排序因此，如果你有你的排序序列并想按序列的顺序输出 @e 属性，你不能使用 $sorted-list/@e，而是你必须使用 for $item in $sorted-list return $item/@e。

参见 http://www.w3.org/TR/xpath20/#id-path-expressions其中说:

Each operation E1/E2 is evaluated as follows: ... If every evaluation of E2 returns a (possibly empty) sequence of nodes, these sequences are combined, and duplicate nodes are eliminated based on node identity. The resulting node sequence is returned in document order.

如果您使用 Saxon 9.5 的商业版本，那么您应该也可以使用 http://www.w3.org/TR/xpath-30/#id-map-operator和 $sorted-list ! @e 保留顺序。

关于xml - 对排序序列的操作不遵守排序顺序，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20435397/