net.sf.saxon.expr
public final class ValueComparison extends BinaryExpression implements ComparisonExpression, Negatable
Constructor Summary | |
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ValueComparison(Expression p1, int op, Expression p2)
Create a relational expression identifying the two operands and the operator
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Method Summary | |
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static boolean | compare(AtomicValue v0, int op, AtomicValue v1, AtomicComparer collator, boolean checkTypes)
Compare two atomic values, using a specified operator and collation
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int | computeCardinality()
Determine the static cardinality. |
boolean | convertsUntypedToOther()
Determine whether untyped atomic values should be converted to the type of the other operand
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Expression | copy()
Copy an expression. |
boolean | effectiveBooleanValue(XPathContext context)
Evaluate the effective boolean value of the expression
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Item | evaluateItem(XPathContext context)
Evaluate the expression in a given context
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protected void | explainExtraAttribute(ExpressionPresenter out) |
AtomicComparer | getAtomicComparer()
Get the AtomicComparer used to compare atomic values. |
ItemType | getItemType(TypeHierarchy th)
Determine the data type of the expression
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BooleanValue | getResultWhenEmpty()
Get the result to be returned if one of the operands is an empty sequence |
int | getSingletonOperator()
Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT,
Token.FLE, Token.FGE |
boolean | isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable
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boolean | needsRuntimeComparabilityCheck()
Determine whether a run-time check is needed to check that the types of the arguments
are comparable |
Expression | 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(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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void | setAtomicComparer(AtomicComparer comparer)
Set the AtomicComparer used to compare atomic values |
void | setResultWhenEmpty(BooleanValue value)
Set the result to be returned if one of the operands is an empty sequence |
Expression | typeCheck(ExpressionVisitor visitor, 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: v0 the first operand op the operator, as defined by constants such as FEQ or FLT v1 the second operand collator the Collator to be used when comparing strings checkTypes
Returns: the result of the comparison: -1 for LT, 0 for EQ, +1 for GT
Throws: XPathException if the values are not comparable
Returns: true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.
Returns: the copy of the original expression
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 the type hierarchy cache
Returns: Type.BOOLEAN
Returns: BooleanValue.TRUE, BooleanValue.FALSE, or null (meaning the empty sequence)
Returns: true if it is
Returns: true if a run-time check is needed
Returns: the inverted comparison
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: visitor an expression visitor 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: XPathException if an error is discovered during this phase (typically a type error)
Parameters: comparer the AtomicComparer
Parameters: value the result to be returned if an operand is empty. Supply null to mean the empty sequence.