Package net.sf.saxon.expr

## Class HomogeneityChecker

- java.lang.Object
- - net.sf.saxon.expr.Expression
  - - net.sf.saxon.expr.UnaryExpression
    - - net.sf.saxon.expr.HomogeneityChecker

- All Implemented Interfaces:
    `ExportAgent`, `Locatable`, `IdentityComparable`, `Traceable`

      public class HomogeneityChecker
      extends UnaryExpression

  This class is an expression that does a run-time check of the result of a "/" expression to ensure that (a) the results consists entirely of atomic values and function items, or entirely of nodes, and (b) if the results are nodes, then they are deduplicated and sorted into document order.

- - ### Field Summary

    - ### Fields inherited from class net.sf.saxon.expr.Expression

      `EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `HomogeneityChecker​(Expression base)` |

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `Expression` | `copy​(RebindingMap rebindings)` | Copy an expression.
    `java.lang.String` | `getExpressionName()` | Get a name identifying the kind of expression, in terms meaningful to a user.
    `int` | `getImplementationMethod()` | An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
    `protected OperandRole` | `getOperandRole()` | Get the usage (in terms of streamability analysis) of the single operand
    `SequenceIterator` | `iterate​(XPathContext context)` | Iterate the path-expression in a given context
    `Expression` | `optimize​(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)` | Perform optimisation of an expression and its subexpressions.
    `Pattern` | `toPattern​(Configuration config)` | Convert this expression to an equivalent XSLT pattern
    `Expression` | `typeCheck​(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)` | Type-check the expression.

    - ### Methods inherited from class net.sf.saxon.expr.UnaryExpression

      `computeCardinality, computeHashCode, computeSpecialProperties, displayOperator, emitExtraAttributes, equals, export, getBaseExpression, getItemType, getOperand, operands, setBaseExpression, toShortString, toString`

    - ### Methods inherited from class net.sf.saxon.expr.Expression

      `addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, typeCheckChildren, typeError, unordered, verifyParentPointers`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

    - ### Methods inherited from interface net.sf.saxon.trace.Traceable

      `gatherProperties`

- - ### Constructor Detail

    - #### HomogeneityChecker

          public HomogeneityChecker​(Expression base)

  - ### Method Detail

    - #### getOperandRole

          protected OperandRole getOperandRole()

      Description copied from class: `UnaryExpression`
      Get the usage (in terms of streamability analysis) of the single operand
      Specified by:
        `getOperandRole` in class `UnaryExpression`
      Returns:
        the operand usage

    - #### typeCheck

          public Expression typeCheck​(ExpressionVisitor visitor,
                                      ContextItemStaticInfo contextInfo)
                               throws XPathException

      Type-check the expression. Default implementation for unary operators that accept any kind of operand
      Overrides:
        `typeCheck` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextInfo` - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
      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)

    - #### toPattern

          public Pattern toPattern​(Configuration config)
                            throws XPathException

      Convert this expression to an equivalent XSLT pattern
      Overrides:
        `toPattern` in class `Expression`
      Parameters:
        `config` - the Saxon configuration
      Returns:
        the equivalent pattern
      Throws:
        `XPathException` - if conversion is not possible

    - #### optimize

          public Expression optimize​(ExpressionVisitor visitor,
                                     ContextItemStaticInfo contextInfo)
                              throws XPathException

      Description copied from class: `UnaryExpression`
      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.

      Overrides:
        `optimize` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextInfo` - 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 if appropriate to optimize execution
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### copy

          public Expression copy​(RebindingMap rebindings)

      Copy an expression. This makes a deep copy.
      Specified by:
        `copy` in class `Expression`
      Parameters:
        `rebindings` -
      Returns:
        the copy of the original expression

    - #### getImplementationMethod

          public int getImplementationMethod()

      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
      Specified by:
        `getImplementationMethod` in class `Expression`
      Returns:
        the implementation method, for example `Expression.ITERATE_METHOD` or `Expression.EVALUATE_METHOD` or `Expression.PROCESS_METHOD`

    - #### iterate

          public SequenceIterator iterate​(XPathContext context)
                                   throws XPathException

      Iterate the path-expression in a given context
      Overrides:
        `iterate` in class `Expression`
      Parameters:
        `context` - the evaluation context
      Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
      Throws:
        `XPathException` - if any dynamic error occurs evaluating the expression

    - #### getExpressionName

          public java.lang.String getExpressionName()

      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
        `getExpressionName` in class `Expression`
      Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.