Module sorting 

XSLT sorting (§33, §85 Phase 8).

The <xsl:sort> element specifies sort criteria for <xsl:for-each> and <xsl:apply-templates>.

Sorting supports:

• Multiple sort keys (primary, secondary, etc.)
• Text and numeric data types
• Ascending and descending order
• Case-order (upper-first, lower-first)
• Language-specific sorting

UPSTREAM-PARITY

Upstream libxslt (sort.c) sorts node-sets using a qsort-like comparison driven by xsltSortNodeSet. Each _xsltSort holds one sort key with select, lang, data-type, order, and case-order attributes. Multiple sort keys are chained via next, with the first being the primary key.

Comparison semantics:

• data-type="number": numeric comparison (NaN sorts as NaN after all)
• data-type="text": byte-wise string comparison (upstream uses xmlStrcmp, extended by locale-aware comparison when available)
• order="descending" inverts the comparison result

Constants

XSLT_SORT_ASCENDING

Sort order constants

XSLT_SORT_CASE_LOWER_FIRST

XSLT_SORT_CASE_UPPER_FIRST

Case order constants

XSLT_SORT_DESCENDING

XSLT_SORT_NUMBER

XSLT_SORT_TEXT

Sort data type constants

Functions

xsltCompareNodes^⚠

Compare two nodes according to a chain of sort specifications.

xsltCompareSingle^⚠

Compare two nodes according to a single sort key.

xsltCompileSort^⚠

Compile a sort specification from an xsl:sort instruction node.

xsltFreeSort^⚠

Free a sort specification.

xsltFreeSortList^⚠

Free a chain of sort specifications.

xsltSortNodeSet^⚠

Sort a node-set according to the sort specifications.