net.sf.saxon.expr
public final class ValueComparison extends BinaryExpression
Constructor Summary | |
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ValueComparison(Expression p1, int op, Expression p2)
Create a relational expression identifying the two operands and the operator |
Method Summary | |
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static boolean | compare(AtomicValue v1, int op, AtomicValue v2, AtomicComparer collator)
Compare two atomic values, using a specified operator and collation |
int | computeCardinality()
Determine the static cardinality. |
protected String | displayOperator() |
boolean | effectiveBooleanValue(XPathContext context)
Evaluate the effective boolean value of the expression |
Item | evaluateItem(XPathContext context)
Evaluate the expression in a given context |
ItemType | getItemType(TypeHierarchy th)
Determine the data type of the expression |
BooleanValue | getResultWhenEmpty()
Get the result to be returned if one of the operands is an empty sequence |
ValueComparison | negate()
Return the negation of this value comparison: that is, a value comparison that returns true()
if and only if the original returns false(). |
Expression | optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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void | setResultWhenEmpty(BooleanValue value)
Set the result to be returned if one of the operands is an empty sequence |
Expression | typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression |
Parameters: p1 the left-hand operand op the operator, as a token returned by the Tokenizer (e.g. Token.LT) p2 the right-hand operand
Parameters: v1 the first operand op the operator, as defined by constants such as FEQ or FLT v2 the second operand collator the Collator to be used when comparing strings
Throws: net.sf.saxon.trans.DynamicError if the values are not comparable
Parameters: context the given context for evaluation
Returns: a boolean representing the result of the comparison of the two operands
Parameters: context the given context for evaluation
Returns: a BooleanValue representing the result of the numeric comparison of the two operands, or null representing the empty sequence
Parameters: th
Returns: Type.BOOLEAN
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
Parameters: opt the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances. env the static context of the expression contextItemType the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to ITEM_TYPE
Returns: the original expression, rewritten if appropriate to optimize execution
Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)