Class BinaryExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator
Direct Known Subclasses:
ArithmeticExpression, ArithmeticExpression10, BooleanExpression, GeneralComparison, GeneralComparison10, IdentityComparison, RangeExpression, ValueComparison, VennExpression

public abstract class BinaryExpression extends Expression
Binary Expression: a numeric or boolean expression consisting of the two operands and an operator
See Also:
  • Field Details

    • operand0

      protected Expression operand0
    • operand1

      protected Expression operand1
    • operator

      protected int operator
  • Constructor Details

    • BinaryExpression

      public BinaryExpression(Expression p0, int op, Expression p1)
      Create a binary expression identifying the two operands and the operator
      Parameters:
      p0 - the left-hand operand
      op - the operator, as a token returned by the Tokenizer (e.g. Token.AND)
      p1 - the right-hand operand
  • Method Details

    • simplify

      public Expression simplify(ExpressionVisitor visitor) throws XPathException
      Simplify an expression
      Overrides:
      simplify in class Expression
      Parameters:
      visitor - an expression visitor
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Type-check the expression. Default implementation for binary operators that accept any kind of operand
      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)
    • optimize

      public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      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 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 if appropriate to optimize execution
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)
    • setFlattened

      public void setFlattened(boolean flattened)
      Mark an expression as being "flattened". This is a collective term that includes extracting the string value or typed value, or operations such as simple value construction that concatenate text nodes before atomizing. The implication of all of these is that although the expression might return nodes, the identity of the nodes has no significance. This is called during type checking of the parent expression.
      Overrides:
      setFlattened in class Expression
      Parameters:
      flattened - set to true if the result of the expression is atomized or otherwise turned into an atomic value
    • promote

      public Expression promote(PromotionOffer offer, Expression parent) throws XPathException
      Promote this expression if possible
      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
    • iterateSubExpressions

      public Iterator<Expression> iterateSubExpressions()
      Get the immediate subexpressions of this expression
      Overrides:
      iterateSubExpressions in class Expression
      Returns:
      an iterator containing the sub-expressions of this expression
    • getArguments

      public Expression[] getArguments()
      Get the subexpressions (arguments to this expression)
      Returns:
      the arguments, as an array
    • replaceSubExpression

      public boolean replaceSubExpression(Expression original, Expression replacement)
      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
    • getOperator

      public int getOperator()
      Get the operator
      Returns:
      the operator, for example Token.PLUS
    • getOperands

      public Expression[] getOperands()
      Get the operands
      Returns:
      the two operands of the binary expression, as an array of length 2
    • computeCardinality

      public int computeCardinality()
      Determine the static cardinality. Default implementation returns [0..1] if either operand can be empty, or [1..1] otherwise.
      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
    • computeSpecialProperties

      public int computeSpecialProperties()
      Determine the special properties of this expression
      Overrides:
      computeSpecialProperties in class Expression
      Returns:
      StaticProperty.NON_CREATIVE. This is overridden for some subclasses.
    • isCommutative

      protected static boolean isCommutative(int operator)
      Determine whether a binary operator is commutative, that is, A op B = B op A.
      Parameters:
      operator - the operator, for example Token.PLUS
      Returns:
      true if the operator is commutative
    • isAssociative

      protected static boolean isAssociative(int operator)
      Determine whether an operator is associative, that is, ((a^b)^c) = (a^(b^c))
      Parameters:
      operator - the operator, for example Token.PLUS
      Returns:
      true if the operator is associative
    • isInverse

      protected static boolean isInverse(int op1, int op2)
      Test if one operator is the inverse of another, so that (A op1 B) is equivalent to (B op2 A). Commutative operators are the inverse of themselves and are therefore not listed here.
      Parameters:
      op1 - the first operator
      op2 - the second operator
      Returns:
      true if the operators are the inverse of each other
    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class Object
    • hashCode

      public int hashCode()
      Get a 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.
      Overrides:
      hashCode in class Object
    • 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
      Overrides:
      toString in class Expression
      Returns:
      a representation of the expression as a string
    • explain

      public void explain(ExpressionPresenter out)
      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 output destination for the displayed expression tree
    • explainExtraAttributes

      protected void explainExtraAttributes(ExpressionPresenter out)
      Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.
      Parameters:
      out - the output destination for the displayed expression tree
    • displayOperator

      protected String displayOperator()
      Display the operator used by this binary expression
      Returns:
      String representation of the operator (for diagnostic display only)