Package edu.caltech.nanodb.expressions

Class NegateOperator

  • All Implemented Interfaces:
    java.lang.Cloneable
    public class NegateOperator
extends Expression
    This class implements unary negation.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private Expression expr
      The expression being negated.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected java.lang.Object clone()
      Creates a copy of expression.
      boolean equals​(java.lang.Object obj)
      Checks if the argument is an expression with the same structure, but not necesarily the same references.
      java.lang.Object evaluate​(Environment env)
      Evaluates this expression object in the context of the specified environment.
      ColumnInfo getColumnInfo​(Schema schema)
      Returns a ColumnInfo object describing the type (and possibly the name) of the expression's result.
      int hashCode()
      Computes the hashcode of an Expression.
      Expression simplify()
      Simplifies an arithmetic expression, computing as much of the expression as possible.
      java.lang.String toString()
      Returns a string representation of this arithmetic expression and its subexpressions, including parentheses where necessary to specify precedence.
      Expression traverse​(ExpressionProcessor p)
      This method allows the entire expression tree to be traversed node by node, either for analysis or for transformation.

      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait

    • Field Detail

      • expr

        private Expression expr
        The expression being negated.

    • Constructor Detail

      • NegateOperator

        public NegateOperator​(Expression e)

    • Method Detail

      • getColumnInfo

        public ColumnInfo getColumnInfo​(Schema schema)
                         throws SchemaNameException
        Description copied from class: Expression
        Returns a ColumnInfo object describing the type (and possibly the name) of the expression's result.
        Specified by:
        getColumnInfo in class Expression
        Parameters:
        schema - a schema object that can be used to look up name and type details for symbols referenced by the expression.
        Returns:
        a column-information object describing the type (and possibly the name and table-name) of this expression's result
        Throws:
        SchemaNameException - if a symbol cannot be resolved, either because it doesn't appear in the schema, or because the name is ambiguous.

      • evaluate

        public java.lang.Object evaluate​(Environment env)
                          throws ExpressionException
        Description copied from class: Expression
        Evaluates this expression object in the context of the specified environment. The environment provides any external information necessary to evaluate the expression, such as the current tuples loaded from tables referenced within the expression.
        Specified by:
        evaluate in class Expression
        Parameters:
        env - the environment to look up symbol-values from, when evaluating the expression
        Returns:
        the result of the expression evaluation
        Throws:
        ExpressionException - if the expression cannot be evaluated for some reason.

      • traverse

        public Expression traverse​(ExpressionProcessor p)
        Description copied from class: Expression

        This method allows the entire expression tree to be traversed node by node, either for analysis or for transformation. The ExpressionProcessor instance receives notifications as each node in the expression is entered and left.

        The expression tree can also be manipulated by this traversal process, depending on what the ExpressionProcessor wants to do. If the expression node that traverse() is invoked on, needs to be replaced with a new expression node, the replacement is returned by the traverse() method. (The ExpressionProcessor specifies the replacement as the return-value from the ExpressionProcessor.leave(Expression) method.)

        Specified by:
        traverse in class Expression
        Parameters:
        p - the object that performs analysis or transformation of the expression tree
        Returns:
        an Expression node to replace this node, or null if no changes are to be made.

      • toString

        public java.lang.String toString()
        Returns a string representation of this arithmetic expression and its subexpressions, including parentheses where necessary to specify precedence.
        Overrides:
        toString in class java.lang.Object

      • simplify

        public Expression simplify()
        Simplifies an arithmetic expression, computing as much of the expression as possible.
        Overrides:
        simplify in class Expression
        Returns:
        a reference to an expression, either a simplified version of this expression, or the original unmodified expression

      • equals

        public boolean equals​(java.lang.Object obj)
        Checks if the argument is an expression with the same structure, but not necesarily the same references.
        Specified by:
        equals in class Expression
        Parameters:
        obj - the object to which we are comparing

      • hashCode

        public int hashCode()
        Computes the hashcode of an Expression. This method is used to see if two expressions CAN be equal.
        Specified by:
        hashCode in class Expression

      • clone

        protected java.lang.Object clone()
                          throws java.lang.CloneNotSupportedException
        Creates a copy of expression.
        Overrides:
        clone in class Expression
        Throws:
        java.lang.CloneNotSupportedException