com.saxonica.functions.hof
Class PartialApply

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by com.saxonica.functions.hof.PartialApply
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

public class PartialApply
extends Expression

This expression class implements the operation of currying (or performing partial application) of a function. That is, it takes a function and a set of argument bindings as input, and produces a new function as output.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.Expression
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
PartialApply(Expression base, Expression[] boundArguments)
          Create a partial function application expression
 
Method Summary
protected  int computeCardinality()
          Compute the static cardinality of this expression
 Expression copy()
          Copy an expression.
 Item evaluateItem(XPathContext context)
          Evaluate this experssion at run-time
 void explain(ExpressionPresenter out)
          Diagnostic print of expression structure.
 Expression getBaseExpression()
           
 Expression[] getBoundArguments()
           
 ItemType getItemType(TypeHierarchy th)
          Determine the data type of the expression, if possible.
 Iterator<Expression> iterateSubExpressions()
          Get the immediate sub-expressions of this expression.
 Expression promote(PromotionOffer offer, Expression parent)
          Offer promotion for this subexpression.
 boolean replaceSubExpression(Expression original, Expression replacement)
          Replace one subexpression by a replacement subexpression
 Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
          Perform type checking of an expression and its subexpressions.
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, optimize, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

PartialApply

public PartialApply(Expression base,
                    Expression[] boundArguments)
Create a partial function application expression

Parameters:
base - the expression that returns the function to be called
boundArguments - an array in which each element is either an expression to be bound to the corresponding argument, or null to represent a placeholder ("?" in the source syntax)
Method Detail

getBaseExpression

public Expression getBaseExpression()

getBoundArguments

public Expression[] getBoundArguments()

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException
Description copied from class: Expression
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:
typeCheck in class Expression
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 Type.ITEM_TYPE
Returns:
the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

getItemType

public ItemType getItemType(TypeHierarchy th)
Description copied from class: Expression
Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Specified by:
getItemType in class Expression
Parameters:
th - the type hierarchy cache
Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()
Description copied from class: Expression
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Overrides:
iterateSubExpressions in class Expression
Returns:
an iterator containing the sub-expressions of this expression

promote

public Expression promote(PromotionOffer offer,
                          Expression parent)
                   throws XPathException
Description copied from class: Expression
Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

This method must be overridden for any Expression that has subexpressions.

Overrides:
promote in class Expression
Parameters:
offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
parent - the containing expression in the expression tree
Returns:
if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
Throws:
XPathException - if any error is detected

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Description copied from class: Expression
Replace one subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

explain

public void explain(ExpressionPresenter out)
Description copied from class: Expression
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:
explain in class Expression
Parameters:
out - the expression presenter used to display the structure

computeCardinality

protected int computeCardinality()
Description copied from class: Expression
Compute the static cardinality of this expression

Specified by:
computeCardinality in class Expression
Returns:
the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

copy

public Expression copy()
Description copied from class: Expression
Copy an expression. This makes a deep copy.

Specified by:
copy in class Expression
Returns:
the copy of the original expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate this experssion at run-time

Overrides:
evaluateItem in class Expression
Parameters:
context - The XPath dynamic evaluation context
Returns:
the result of the function, or null to represent an empty sequence
Throws:
XPathException - if a dynamic error occurs during evaluation of the function.


Copyright (c) 2004-2011 Saxonica Limited. All rights reserved.