net.sf.saxon.expr

Class UnaryExpression

public abstract class UnaryExpression extends Expression

Unary Expression: an expression taking a single operand expression
Field Summary
protected Expressionoperand
Constructor Summary
UnaryExpression(Expression p0)
Method Summary
intcomputeCardinality()
Determine the static cardinality.
intcomputeSpecialProperties()
Get the static properties of this expression (other than its type).
protected StringdisplayExpressionName()
Return the element name to use in the expression tree
protected StringdisplayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics
booleanequals(Object other)
Is this expression the same as another expression?
voidexplain(ExpressionPresenter out)
Diagnostic print of expression structure.
ExpressiongetBaseExpression()
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
inthashCode()
get HashCode for comparing two expressions.
Iterator<Expression>iterateSubExpressions()
Get the immediate subexpressions of this expression
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionpromote(PromotionOffer offer, Expression parent)
Promote this expression if possible
booleanreplaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
Expressionsimplify(ExpressionVisitor visitor)
Simplify an expression
StringtoString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression.

Field Detail

operand

protected Expression operand

Constructor Detail

UnaryExpression

public UnaryExpression(Expression p0)

Method Detail

computeCardinality

public int computeCardinality()
Determine the static cardinality. Default implementation returns the cardinality of the operand

computeSpecialProperties

public int computeSpecialProperties()
Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

displayExpressionName

protected String displayExpressionName()
Return the element name to use in the expression tree

displayOperator

protected String displayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics

Parameters: config

Returns: the operator, as a string

equals

public boolean equals(Object other)
Is this expression the same as another expression?

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

getBaseExpression

public Expression getBaseExpression()

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible. The default implementation for unary expressions returns the item type of the operand

Parameters: th the type hierarchy cache

Returns: the item type of the items in the result sequence, insofar as this is known statically.

hashCode

public int hashCode()
get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()
Get the immediate subexpressions of this expression

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.

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)

promote

public Expression promote(PromotionOffer offer, Expression parent)
Promote this expression if possible

replaceSubExpression

public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression

Parameters: original the original subexpression replacement the replacement subexpression

Returns: true if the original subexpression is found

simplify

public Expression simplify(ExpressionVisitor visitor)
Simplify an expression

Parameters: visitor an expression visitor

Returns: the simplified expression

toString

public String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression. Default implementation for unary operators that accept any kind of operand