Mihaela Mihaljevic
d83e5a88ce
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
57 lines
2.6 KiB
Swift
57 lines
2.6 KiB
Swift
public extension PureXML.XPath {
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/// A compiled XPath 1.0 expression: all thirteen axes with their
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/// abbreviations, the node tests, the operator grammar (`or`, `and`, `=`,
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/// `!=`, `<`, `<=`, `>`, `>=`, `+`, `-`, `*`, `div`, `mod`, unary `-`, `|`),
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/// number and string literals, variable references, function calls, and
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/// filter expressions, all over the four-type model (node-set, boolean,
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/// number, string). Reimplemented from the XPath 1.0 specification.
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struct Query: Sendable {
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let expression: Expression
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/// Compiles an XPath expression, throwing ``QueryError`` on a syntax error.
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public init(_ path: String) throws {
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expression = try Compiler.compile(path)
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}
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/// Evaluates the query over a node, returning the selected node-set in
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/// document order. A non-node-set expression yields an empty list; use
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/// ``value(over:variables:)`` for typed results.
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public func evaluate(over node: PureXML.Model.Node) -> [Selection] {
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Evaluator.evaluate(expression, over: node)
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}
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/// Evaluates the query and returns the selected elements only.
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public func elements(over node: PureXML.Model.Node) -> [PureXML.Model.Element] {
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evaluate(over: node).compactMap(\.element)
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}
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/// Evaluates the query and returns the string-value of each selection.
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public func strings(over node: PureXML.Model.Node) -> [String] {
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evaluate(over: node).map(\.stringValue)
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}
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/// Evaluates the query to a typed ``Value`` with optional variable bindings.
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public func value(
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over node: PureXML.Model.Node,
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variables: [String: Value] = [:],
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) throws -> Value {
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try Evaluator.value(expression, over: node, variables: variables)
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}
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/// Evaluates the query and coerces the result to a number.
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public func number(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> Double {
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try value(over: node, variables: variables).number
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}
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/// Evaluates the query and coerces the result to a string.
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public func string(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> String {
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try value(over: node, variables: variables).string
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}
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/// Evaluates the query and coerces the result to a boolean.
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public func boolean(over node: PureXML.Model.Node, variables: [String: Value] = [:]) throws -> Bool {
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try value(over: node, variables: variables).boolean
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}
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}
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}
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