Package com.singularsys.extensions.stream

Class StreamFold

java.lang.Object

com.singularsys.jep.functions.PostfixMathCommand

com.singularsys.jep.functions.BinaryFunction

com.singularsys.extensions.stream.StreamFold

All Implemented Interfaces:

ZeroLengthBehaviourI, ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI, JepComponent, PostfixMathCommandI, Serializable

public class StreamFold
extends BinaryFunction
implements JepComponent, ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Fold a list using a lambda function to reduce the list down to a single argument.

 Sum = [x,y]=>x+y
 fold(Sum, [1,2,3,4,5])
 

If the stream has a single element, then that element is returned without applying the lambda function.

By default, if the stream is empty, an exception is thrown, but the behaviour can be configured using the methods of the ZeroLengthBehaviourI interface.

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class com.singularsys.jep.functions.BinaryFunction

BinaryFunction.BiFunctionWithException<T>

Nested classes/interfaces inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI

ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI, ZeroLengthBehaviourI.ZeroLengthErrorBehaviour, ZeroLengthBehaviourI.ZeroLengthHelper

Field Summary

Fields inherited from class com.singularsys.jep.functions.PostfixMathCommand

curNumberOfParameters, description, name, NaN, numberOfParameters

Constructor Summary

Constructors

Constructor	Description
StreamFold()	Default constructor with no zero length array handling, i.e. an exception is thrown when a zero length array is passed as an argument.

Method Summary

Modifier and Type	Method	Description
Object	eval(Object l, Object r)	Evaluate the function
JepComponent	getLightWeightInstance()	Gets a light-weight instance suitable for using in multiple threads.
ZeroLengthBehaviourI	getZeroLengthHelper()	Gets the helper class which implements the zero length behaviour.
void	init(Jep jep)	Initialize the component.

Methods inherited from class com.singularsys.jep.functions.BinaryFunction

instanceOf, instanceOf, instanceOf, instanceOf, run

Methods inherited from class com.singularsys.jep.functions.PostfixMathCommand

asArray, asBool, asDouble, asInt, asLong, asStrictInt, asString, asType, checkNumberOfParameters, getDescription, getDescription, getDescriptionWithType, getName, getNumberOfParameters, setCurNumberOfParameters, setDescription, setName, toString, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI

getErrorMessage, getValueOrException, zeroLengthResultOrException

Methods inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

getZeroLengthErrorBehaviour, getZeroLengthValue, setZeroLengthErrorBehaviour, setZeroLengthValue

Constructor Details

StreamFold

public StreamFold()

Default constructor with no zero length array handling, i.e. an exception is thrown when a zero length array is passed as an argument.

Method Details

eval

public Object eval(Object l,
 Object r)
            throws EvaluationException

Description copied from class: BinaryFunction

Evaluate the function

Specified by:

eval in class BinaryFunction

Parameters:

l - lhs argument

r - rhs argument

Returns:

the results

Throws:

EvaluationException - if the function cannot be evaluated.

init

public void init(Jep jep)

Description copied from interface: JepComponent

Initialize the component. This method is called whenever a component is added to Jep. Hence, it allows components to keep track of the other components they may rely on.

Specified by:

init in interface JepComponent

Parameters:

jep - the current Jep instance

getLightWeightInstance

public JepComponent getLightWeightInstance()

Description copied from interface: JepComponent

Gets a light-weight instance suitable for using in multiple threads.

Specified by:

getLightWeightInstance in interface JepComponent

Returns:

either a new instance, null or 'this'.

getZeroLengthHelper

public ZeroLengthBehaviourI getZeroLengthHelper()

Description copied from interface: ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Gets the helper class which implements the zero length behaviour. The standard implementation is:

ZeroLengthHelper zeroLengthHelper = new ZeroLengthHelper();
@Override
public ZeroLengthBehaviourI getZeroLengthHelper() {
    return zeroLengthHelper;
}

Specified by:

getZeroLengthHelper in interface ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Returns:

the helper class