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 $variable binding map; the core functions last, position, count, not, true, false, boolean, number, and string ship with it. Closes #42
33 lines
1.5 KiB
Swift
33 lines
1.5 KiB
Swift
public extension PureXML.XPath {
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/// An error compiling or evaluating an XPath query.
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enum QueryError: Swift.Error, Equatable, Sendable, CustomStringConvertible {
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case empty
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case unexpectedToken(String)
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case expectedNodeTest
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case unterminatedPredicate
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case unsupportedPredicate(String)
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/// An axis name was not one of the thirteen XPath axes.
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case unsupportedAxis(String)
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/// A function was called that is not in the library.
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case unknownFunction(String)
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/// A `$name` reference had no binding in the evaluation context.
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case undefinedVariable(String)
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/// A function received the wrong number or type of arguments.
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case invalidArguments(String)
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public var description: String {
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switch self {
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case .empty: "the XPath expression is empty"
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case let .unexpectedToken(token): "unexpected token '\(token)'"
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case .expectedNodeTest: "expected a node test"
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case .unterminatedPredicate: "unterminated predicate"
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case let .unsupportedPredicate(detail): "unsupported predicate: \(detail)"
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case let .unsupportedAxis(axis): "unsupported axis: \(axis)"
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case let .unknownFunction(name): "unknown function '\(name)()'"
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case let .undefinedVariable(name): "variable '$\(name)' is not bound"
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case let .invalidArguments(detail): "invalid arguments: \(detail)"
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}
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}
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}
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}
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