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## com.saxonica.functions.hof
Class PartialApply

    java.lang.Object
      net.sf.saxon.expr.Expression
          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.

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