uk.ac.starlink.ttools.jel

Class RandomJELEvaluator

java.lang.Object

uk.ac.starlink.ttools.jel.RandomJELEvaluator

All Implemented Interfaces:

Closeable, AutoCloseable

public abstract class RandomJELEvaluator
extends Object
implements Closeable

Random-access evaluator for JEL expressions evaluated against tables.

Since:

11 Dec 2020

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
RandomJELEvaluator()

Method Summary

Modifier and Type	Method and Description
static RandomJELEvaluator	createEvaluator(StarTable table, 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 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 Object evaluateObject(long lrow)
                               throws 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:

IOException

evaluateDouble

public abstract double evaluateDouble(long lrow)
                               throws 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:

IOException

evaluateBoolean

public abstract boolean evaluateBoolean(long lrow)
                                 throws 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:

IOException

createEvaluator

public static RandomJELEvaluator createEvaluator(StarTable table,
                                                 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