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
44 lines
1.5 KiB
Swift
44 lines
1.5 KiB
Swift
extension PureXML.XPath {
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/// A binary operator of the XPath expression language, grouped by the
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/// precedence level its parser method handles.
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enum BinaryOperator: Equatable {
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case logicalOr
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case logicalAnd
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case equal
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case notEqual
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case lessThan
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case lessOrEqual
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case greaterThan
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case greaterOrEqual
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case add
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case subtract
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case multiply
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case divide
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case modulo
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}
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/// A compiled XPath expression. A bare location path is ``path``; the operator
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/// grammar, function calls, variables, and filter expressions build on it.
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indirect enum Expression: Equatable, Sendable {
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/// A location path: absolute when rooted, with its ordered steps.
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case path(absolute: Bool, steps: [Step])
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/// A binary operation.
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case binary(BinaryOperator, Expression, Expression)
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/// Unary minus.
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case negate(Expression)
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/// A node-set union (`|`).
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case union(Expression, Expression)
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/// A numeric literal.
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case number(Double)
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/// A string literal.
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case string(String)
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/// A function call.
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case function(name: String, arguments: [Expression])
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/// A variable reference (`$name`).
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case variable(String)
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/// A primary expression with predicates and an optional trailing path
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/// (`(expr)[p]/step`, `id('x')/step`).
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case filter(primary: Expression, predicates: [Expression], steps: [Step])
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}
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}
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