uk.ac.starlink.topcat

Class TopcatJELEvaluator

java.lang.Object

uk.ac.starlink.topcat.TopcatJELEvaluator

All Implemented Interfaces:

Closeable, AutoCloseable

public abstract class TopcatJELEvaluator
extends Object
implements Closeable

Random-access evaluator for a JEL expression evaluated against a TopcatModel.

Note this is more or less a copy of RandomJELEvaluator. It's very difficult to make that code reusable here because this class needs to use a TopcatJELRowReader rather than a StarTableRowReader (enhanced expression parsing, e.g. RowSubsets) and the differing functionality is implemented using inheritance rather than composition. The right thing would probably be to rework the JEL usage to use composition, but it's not straightforward. Live with duplicated code instead.

Since:

11 Dec 2020

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
TopcatJELEvaluator()

Method Summary

Modifier and Type	Method and Description
static TopcatJELEvaluator	createEvaluator(TopcatModel tcModel, String expr, boolean activation, Class<?> reqType) Returns a TopcatJELEvaluator 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.
abstract String	getExpression() Returns the text of the expression that this evaluator can evaluate.
abstract Class<?>	getResultType() Returns the actual result type that JEL has determined the compiled expression to have.

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

TopcatJELEvaluator

public TopcatJELEvaluator()

Method Detail

getExpression

public abstract String getExpression()

Returns the text of the expression that this evaluator can evaluate.

Returns:

expression

getResultType

public abstract Class<?> getResultType()

Returns the actual result type that JEL has determined the compiled expression to have. This will be (at least compatible with) the return type of the evaluations. It will return wrapper types, not primitive types.

Returns:

non-primitive result type

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 TopcatJELEvaluator createEvaluator(TopcatModel tcModel,
                                                 String expr,
                                                 boolean activation,
                                                 Class<?> reqType)
                                          throws gnu.jel.CompilationException

Returns a TopcatJELEvaluator instance for a given table and expression. The returned implementation is suitable for use from multiple threads concurrently.

Parameters:

tcModel - context for expression evaluation

expr - JEL expression

activation - true to include activation functions

reqType - required result type, or null to accept any

Returns:

evaluator safe for concurrent use

Throws:

gnu.jel.CompilationException - if the expression doesn't compile or doesn't have the (non-null) required type