net.sf.saxon.expr

Class UnaryExpression

public abstract class UnaryExpression extends ComputedExpression

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).
voiddisplay(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure
protected abstract StringdisplayOperator(NamePool pool)
Give a string representation of the operator for use in diagnostics
booleanequals(Object other)
Is this expression the same as another expression?
ExpressiongetBaseExpression()
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
inthashCode()
get HashCode for comparing two expressions.
IteratoriterateSubExpressions()
Get the immediate subexpressions of this expression
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionpromote(PromotionOffer offer)
Promote this expression if possible
Expressionsimplify(StaticContext env)
Simplify an expression
ExpressiontypeCheck(StaticContext env, 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.

display

public void display(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure

displayOperator

protected abstract String displayOperator(NamePool pool)
Give a string representation of the operator for use in diagnostics

Returns: the operator, as a string

equals

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

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

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 iterateSubExpressions()
Get the immediate subexpressions of this expression

optimize

public Expression optimize(Optimizer opt, StaticContext env, 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: 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)

promote

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

simplify

public Expression simplify(StaticContext env)
Simplify an expression

Returns: the simplified expression

typeCheck

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