Compile and evaluate full XPath 1.0 expressions, not just location paths.
Add the four-type Value (node-set, boolean, number, string) with the spec's
coercion rules and canonical number formatting, a recursive-descent parser
for the operator grammar (or/and, equality, relational, additive,
multiplicative, unary minus, union) whose grammatical position disambiguates
* and the operator keywords, function calls, variable references, and filter
expressions. Predicates are now arbitrary expressions (a numeric predicate
is a position test). Comparison follows the node-set quantification rules.
Query gains value/number/string/boolean accessors and a $variable binding
map; the core functions last, position, count, not, true, false, boolean,
number, and string ship with it.
Closes#42
Add PureXML.XPath: a compiled location-path query engine reimplemented from the
XPath 1.0 specification; no upstream code copied.
- Compiler parses a path into steps; Evaluator walks the tree returning a
Selection node-set (node or attribute) in document order.
- Forward axes only (child, descendant //, self ., attribute @), since the value
model has no parent pointers. Node tests: name, *, text(), node(), comment().
Predicates: [n], [@a], [@a='v'], [child], [child='v'].
- Public surface: XPath.Query (init compiles, evaluate/elements/strings), the
Selection enum (element / stringValue), QueryError, and the one-shot
PureXML.xpath(_:over:). Upward/sibling axes and the full expression language
are explicitly out of scope.
- 12 XPath tests; 61 total.
