Package uk.ac.starlink.ttools.jel

Class RandomJELEvaluator

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    public abstract class RandomJELEvaluator
extends java.lang.Object
implements java.io.Closeable
    Random-access evaluator for JEL expressions evaluated against tables.
    Since:
    11 Dec 2020
    Author:
    Mark Taylor

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      static RandomJELEvaluator createEvaluator​(uk.ac.starlink.table.StarTable table, java.lang.String expr, boolean isConcurrent)
      Returns a RandomJELEvaluator instance for a given table and expression.
      abstract boolean evaluateBoolean​(long lrow)
      Returns the value of the expression at a given table row as a boolean.
      abstract double evaluateDouble​(long lrow)
      Returns the value of the expression at a given table row as a double.
      abstract java.lang.Object evaluateObject​(long lrow)
      Returns the value of the expression at a given table row as an Object.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

      • Methods inherited from interface java.io.Closeable

        close

    • Constructor Detail

      • RandomJELEvaluator

        public RandomJELEvaluator()

    • Method Detail

      • evaluateObject

        public abstract java.lang.Object evaluateObject​(long lrow)
                                         throws java.io.IOException
        Returns the value of the expression at a given table row as an Object.
        Parameters:
        lrow - evaluation row index
        Returns:
        object value at given row
        Throws:
        java.io.IOException

      • evaluateDouble

        public abstract double evaluateDouble​(long lrow)
                               throws java.io.IOException
        Returns the value of the expression at a given table row as a double. Behaviour is undefined if the expression is not numeric.
        Parameters:
        lrow - evaluation row index
        Returns:
        numeric value at given row
        Throws:
        java.io.IOException

      • evaluateBoolean

        public abstract boolean evaluateBoolean​(long lrow)
                                 throws java.io.IOException
        Returns the value of the expression at a given table row as a boolean. Behaviour is undefined if the expression is not boolean-typed.
        Parameters:
        lrow - evaluation row index
        Returns:
        boolean value at given row
        Throws:
        java.io.IOException

      • createEvaluator

        public static RandomJELEvaluator createEvaluator​(uk.ac.starlink.table.StarTable table,
                                                 java.lang.String expr,
                                                 boolean isConcurrent)
                                          throws gnu.jel.CompilationException
        Returns a RandomJELEvaluator instance for a given table and expression. The returned implementation may or may not be suitable for use from multiple threads concurrently, depending on the isConcurrent parameter.
        Parameters:
        table - context for expression evaluation
        expr - JEL expression
        isConcurrent - whether result will be suitable for concurrent use
        Returns:
        evaluator, which is only guaranteed safe for concurrent use if isConcurrent was set true
        Throws:
        gnu.jel.CompilationException