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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.BinaryExpression net.sf.saxon.expr.ValueComparison
public final class ValueComparison
ValueComparison: a boolean expression that compares two atomic values for equals, not-equals, greater-than or less-than. Implements the operators eq, ne, lt, le, gt, ge
Field Summary |
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Fields inherited from class net.sf.saxon.expr.BinaryExpression |
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operand0, operand1, operator |
Fields inherited from class net.sf.saxon.expr.Expression |
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EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
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ValueComparison(Expression p1,
int op,
Expression p2)
Create a comparison expression identifying the two operands and the operator |
Method Summary | |
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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 |
Expression |
copy()
Copy an expression. |
boolean |
effectiveBooleanValue(XPathContext context)
Evaluate the effective boolean value of the expression |
Item |
evaluateItem(XPathContext context)
Evaluate the expression in a given context |
protected void |
explainExtraAttribute(ExpressionPresenter out)
|
AtomicComparer |
getAtomicComparer()
Get the AtomicComparer used to compare atomic values. |
String |
getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user. |
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 |
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 |
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,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
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,
ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression |
Methods inherited from class net.sf.saxon.expr.BinaryExpression |
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computeSpecialProperties, displayOperator, equals, explain, explainExtraAttributes, getArguments, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, promote, replaceSubExpression, setFlattened, simplify, toString |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Methods inherited from interface net.sf.saxon.expr.ComparisonExpression |
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getOperands |
Constructor Detail |
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public ValueComparison(Expression p1, int op, Expression p2)
p1
- the left-hand operandop
- the operator, as a token returned by the Tokenizer (e.g. Token.LT)p2
- the right-hand operandMethod Detail |
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public String getExpressionName()
getExpressionName
in class Expression
public void setAtomicComparer(AtomicComparer comparer)
comparer
- the AtomicComparerpublic AtomicComparer getAtomicComparer()
getAtomicComparer
in interface ComparisonExpression
public int getSingletonOperator()
getSingletonOperator
in interface ComparisonExpression
public boolean convertsUntypedToOther()
convertsUntypedToOther
in interface ComparisonExpression
public void setResultWhenEmpty(BooleanValue value)
value
- the result to be returned if an operand is empty. Supply null to mean the empty sequence.public BooleanValue getResultWhenEmpty()
public boolean needsRuntimeComparabilityCheck()
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
typeCheck
in class BinaryExpression
visitor
- an expression visitorcontextItemType
- 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
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
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.
optimize
in class BinaryExpression
visitor
- an expression visitorcontextItemType
- 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
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)public boolean isNegatable(ExpressionVisitor visitor)
isNegatable
in interface Negatable
public Expression negate()
negate
in interface Negatable
public Expression copy()
copy
in class Expression
public boolean effectiveBooleanValue(XPathContext context) throws XPathException
effectiveBooleanValue
in class Expression
context
- the given context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionpublic Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in class Expression
context
- the given context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionpublic ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public int computeCardinality()
computeCardinality
in class BinaryExpression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
protected void explainExtraAttribute(ExpressionPresenter out)
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