org.qtitools.qti.node.expression
Class AbstractExpression

java.lang.Object
  org.qtitools.qti.node.AbstractNode
      org.qtitools.qti.node.AbstractObject
          org.qtitools.qti.node.expression.AbstractExpression

All Implemented Interfaces:

java.io.Serializable, Expression, ExpressionParent, XmlNode, XmlObject, Validatable

Direct Known Subclasses:

And, AnyN, BaseValue, ContainerSize, Contains, CustomOperator, Delete, Divide, DurationGte, DurationLt, Equal, EqualRounded, FieldValue, Gt, Gte, Index, Inside, IntegerDivide, IntegerModulus, IntegerToFloat, IsNull, ItemSubset, LookupExpression, Lt, Lte, MapResponse, MapResponsePoint, Match, Member, Multiple, Not, Null, Or, Ordered, PatternMatch, Power, Product, RandomExpression, RecordEx, Round, StringMatch, Substring, Subtract, Sum, Truncate

public abstract class AbstractExpression
extends AbstractObject
implements Expression

Abstract super class for all expressions.

Author:

Jiri Kajaba

See Also:

Cardinality, BaseType, Serialized Form

Field Summary

protected static org.slf4j.Logger

logger Expression logger.

Fields inherited from interface org.qtitools.qti.node.expression.Expression

DISPLAY_NAME

Fields inherited from interface org.qtitools.qti.node.XmlNode

INDENT, NEW_LINE, SIMPLE_NAME_INNER_SEPARATOR, SIMPLE_NAMES_SEPARATOR

Constructor Summary

AbstractExpression(ExpressionParent parent)
Constructs expression.

Method Summary

Value	evaluate() Evaluates this expression.
protected abstract Value	evaluateSelf(int depth) Evaluates this expression.
BaseType	getBaseType() Gets baseType of evaluated result.
Cardinality	getCardinality() Gets cardinality of evaluated result.
java.util.List<Expression>	getChildren() Gets all children of this expression.
protected Expression	getFirstChild() Returns first subexpression.
ExpressionParent	getParent() Gets parent of this node or null (if node is root; for example AssessmentTest).
protected BaseType[]	getParentRequiredBaseTypes() Gets list of all acceptable baseTypes for this expression from its parent.
protected Cardinality[]	getParentRequiredCardinalities() Gets list of all acceptable cardinalities for this expression from its parent.
BaseType[]	getProducedBaseTypes() Gets list of all possible produced baseTypes after evaluation (possible baseTypes of evaluated result).
Cardinality[]	getProducedCardinalities() Gets list of all possible produced cardinalities after evaluation (possible cardinalities of evaluated result).
protected BaseType[]	getProducedNumericalBaseTypes() Gets list of all possible produced baseTypes after evaluation (possible baseTypes of evaluated result).
BaseType[]	getRequiredBaseTypes(int index) Gets list of all acceptable baseTypes which can child expression at given position produce.
Cardinality[]	getRequiredCardinalities(int index) Gets list of all acceptable cardinalities which can child expression at given position produce.
protected BaseType[]	getRequiredSameBaseTypes(int index, boolean includeParent) Gets list of all acceptable baseTypes which can child expression at given position produce.
protected Cardinality[]	getRequiredSameCardinalities(int index, boolean includeParent) Gets list of all acceptable cardinalities which can child expression at given position produce.
protected Expression	getSecondChild() Returns second subexpression.
ExpressionType	getType() Gets expression type of this expression.
Value	getValue() Gets evaluated result or null if this expression is not evaluated yet.
protected boolean	isAnyChildNull() Returns true if any subexpression is NULL; false otherwise.
boolean	isNull() Returns true if evaluated result of this expression is NULL; false otherwise.
boolean	isVariable() Returns true if value of evaluation can change every evaluation call; false otherwise.
void	reset() Resets this expression and all its children state (set same state like before first evaluation).
java.lang.String	toString()
ValidationResult	validate() Validates this object.

Methods inherited from class org.qtitools.qti.node.AbstractObject

getParentItem, getParentResult, getParentTest, setParent

Methods inherited from class org.qtitools.qti.node.AbstractNode

attrToXmlString, bodyToXmlString, getAttributes, getClassTag, getFullName, getIndent, getNode, getNode, getNode, getNodeGroups, getParentRoot, getSimpleName, getSourceFile, getSourceNode, getSourceString, getSourceUrl, hasChildNodes, load, load, load, load, loadAttributes, readChild, readChildren, setParent, setSourceFile, setSourceNode, setSourceString, setSourceUrl, toXmlString, toXmlString, validateAttributes, validateChildren

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.qtitools.qti.node.XmlObject

getParentItem, getParentResult, getParentTest, setParent

Methods inherited from interface org.qtitools.qti.node.XmlNode

getAttributes, getClassTag, getFullName, getNodeGroups, getParentRoot, getSimpleName, getSourceFile, getSourceNode, getSourceString, getSourceUrl, hasChildNodes, load, load, load, load, setSourceFile, setSourceNode, setSourceString, setSourceUrl, toXmlString, toXmlString

Field Detail

logger

protected static org.slf4j.Logger logger

Expression logger. Used with all expressions.

Constructor Detail

AbstractExpression

public AbstractExpression(ExpressionParent parent)

Constructs expression.

Parameters:

parent - parent of this expression

Method Detail

getParent

public ExpressionParent getParent()

Description copied from interface: XmlNode

Gets parent of this node or null (if node is root; for example AssessmentTest).

While testing some nodes (for example expressions) don't have properly set parent, but it is usable only for testing. (Some nodes cannot exists without parent even for testing).

Specified by:

getParent in interface Expression

Specified by:

getParent in interface XmlNode

Specified by:

getParent in interface XmlObject

Overrides:

getParent in class AbstractObject

Returns:

parent of this node or null (if node is root; for example AssessmentTest)

getType

public ExpressionType getType()

Description copied from interface: Expression

Gets expression type of this expression.

Specified by:

getType in interface Expression

Returns:

expression type of this expression

isVariable

public boolean isVariable()

Description copied from interface: Expression

Returns true if value of evaluation can change every evaluation call; false otherwise. It checks this expression and all of its children (if any child is variable, this expression becomes variable too). Example of variable expressions: variable and outcome expressions.

Specified by:

isVariable in interface Expression

Returns:

true if value of evaluation can change every evaluation call; false otherwise

getRequiredCardinalities

public Cardinality[] getRequiredCardinalities(int index)

Description copied from interface: ExpressionParent

Gets list of all acceptable cardinalities which can child expression at given position produce.

For example delete expression returns single cardinality for index 0 and list of multiple and ordered cardinality for index 1.

Result of this method can change in time.

Static example is expression or. Expression or accepts only single cardinality for any index.

Dynamic example is expression match. Expression match accepts any cardinality of its children, but this cardinality must be same for all its children.

Specified by:

getRequiredCardinalities in interface ExpressionParent

Parameters:

index - position of child expression in this parent

Returns:

list of all possible cardinalities which can child expression at given position produce

getRequiredSameCardinalities

protected Cardinality[] getRequiredSameCardinalities(int index,
                                                     boolean includeParent)

Gets list of all acceptable cardinalities which can child expression at given position produce.

This method is used when same cardinality is required (contains, match).

Parameters:

index - position of child expression in this parent

includeParent - whether parent requirements should be used during calculation

Returns:

list of all acceptable cardinalities which can child expression at given position produce

See Also:

getRequiredCardinalities(int)

getRequiredBaseTypes

public BaseType[] getRequiredBaseTypes(int index)

Description copied from interface: ExpressionParent

Gets list of all acceptable baseTypes which can child expression at given position produce.

Result of this method can change in time.

Static example is expression or. Expression or accepts only boolean baseType for any index.

Dynamic example is expression match. Expression match accepts any baseType of its children. but this baseType must be same for all its children.

Specified by:

getRequiredBaseTypes in interface ExpressionParent

Parameters:

index - position of child expression in this parent

Returns:

list of all acceptable baseTypes which can child expression at given position produce

getRequiredSameBaseTypes

protected BaseType[] getRequiredSameBaseTypes(int index,
                                              boolean includeParent)

Gets list of all acceptable baseTypes which can child expression at given position produce.

This method is used when same baseType is required (contains, delete, index, match, ...).

Parameters:

index - position of child expression in this parent

includeParent - whether parent requirements should be used during calculation

Returns:

list of all acceptable baseTypes which can child expression at given position produce

See Also:

getRequiredBaseTypes(int)

getProducedCardinalities

public Cardinality[] getProducedCardinalities()

Description copied from interface: Expression

Gets list of all possible produced cardinalities after evaluation (possible cardinalities of evaluated result). Result of this method can change in time.

Static example is expression or. Expression or can produce only single cardinality and it cannot change.

Dynamic example is expression variable. Expression variable can produce any cardinality before evaluation. After evaluation it produces cardinality of its result (and it can change every evaluation call!).

Null expression, empty containers (multiple, ordered, record), or NULL values produces all cardinalities. So they are compatible with anything.

Specified by:

getProducedCardinalities in interface Expression

Returns:

list of all possible produced cardinalities after evaluation

getProducedBaseTypes

public BaseType[] getProducedBaseTypes()

Description copied from interface: Expression

Gets list of all possible produced baseTypes after evaluation (possible baseTypes of evaluated result). Result of this method can change in time.

Static example is expression or. Expression or can produce only boolean baseType and it cannot change.

Dynamic example is expression variable. Expression variable can produce any baseType before evaluation. After evaluation it produces baseType of its result (and it can change every evaluation call!).

Null expression, empty containers (multiple, ordered, record), or NULL values produces all baseTypes. So they are compatible with anything.

Specified by:

getProducedBaseTypes in interface Expression

Returns:

list of all possible produced baseTypes after evaluation

getProducedNumericalBaseTypes

protected BaseType[] getProducedNumericalBaseTypes()

Gets list of all possible produced baseTypes after evaluation (possible baseTypes of evaluated result).

This method is used in numerical expressions (product, subtract, sum).

1. if any of children doesn't produce integer nor float, result is empty set
2. if one of children produces only float, result is float
3. if none of all children produces float, result is integer
4. otherwise result is set of integer and float

Returns:

list of all possible produced baseTypes after evaluation (possible baseTypes of evaluated result)

See Also:

getProducedBaseTypes()

getParentRequiredCardinalities

protected Cardinality[] getParentRequiredCardinalities()

Gets list of all acceptable cardinalities for this expression from its parent.

1. evaluates index of this expression in parent
2. calls parent's getRequiredCardinalities(index) method

If this expression doesn't have any parent (it is legal for testing, but not for real use case), returns list of all cardinalities.

Returns:

list of all acceptable cardinalities for this expression from its parent

getParentRequiredBaseTypes

protected BaseType[] getParentRequiredBaseTypes()

Gets list of all acceptable baseTypes for this expression from its parent.

1. evaluates index of this expression in parent
2. calls parent's getRequiredBaseTypes(index) method

If this expression doesn't have any parent (it is legal for testing, but not for real use case), returns list of all baseTypes.

Returns:

list of all acceptable baseTypes for this expression from its parent

validate

public ValidationResult validate()

Description copied from interface: Validatable

Validates this object.

Specified by:

validate in interface Validatable

Overrides:

validate in class AbstractNode

Returns:

validation result

getChildren

public java.util.List<Expression> getChildren()

Description copied from interface: Expression

Gets all children of this expression.

Specified by:

getChildren in interface Expression

Returns:

all children of this expression

isAnyChildNull

protected boolean isAnyChildNull()

Returns true if any subexpression is NULL; false otherwise.

Returns:

true if any subexpression is NULL; false otherwise

getFirstChild

protected Expression getFirstChild()

Returns first subexpression. This is convenient method only. Use this method instead of getChildren().get(0).

Returns:

first subexpression

getSecondChild

protected Expression getSecondChild()

Returns second subexpression. This is convenient method only. Use this method instead of getChildren().get(1).

Returns:

second subexpression

reset

public void reset()

Description copied from interface: Expression

Resets this expression and all its children state (set same state like before first evaluation).

Specified by:

reset in interface Expression

evaluate

public Value evaluate()

Description copied from interface: Expression

Evaluates this expression.

1. evaluates all subexpressions (calls evaluate method for every subexpression)
2. validates this expression (calls validate method)
3. evaluates this expression (calls evaluateSelf method)

Specified by:

evaluate in interface Expression

Returns:

result of evaluation

evaluateSelf

protected abstract Value evaluateSelf(int depth)

Evaluates this expression. All children must be already evaluated. Contains no checks.

Parameters:

depth - depth of this expression in expression tree (root's depth = 0)

Returns:

result of evaluation

isNull

public boolean isNull()
               throws java.lang.NullPointerException

Description copied from interface: Expression

Returns true if evaluated result of this expression is NULL; false otherwise.

Specified by:

isNull in interface Expression

Returns:

true if evaluated result of this expression is NULL; false otherwise

Throws:

java.lang.NullPointerException - if this expression is not evaluated yet

getCardinality

public Cardinality getCardinality()
                           throws java.lang.NullPointerException

Description copied from interface: Expression

Gets cardinality of evaluated result.

Specified by:

getCardinality in interface Expression

Returns:

cardinality of evaluated result

Throws:

java.lang.NullPointerException - if this expression is not evaluated yet

getBaseType

public BaseType getBaseType()
                     throws java.lang.NullPointerException

Description copied from interface: Expression

Gets baseType of evaluated result.

Specified by:

getBaseType in interface Expression

Returns:

baseType of evaluated result

Throws:

java.lang.NullPointerException - if this expression is not evaluated yet

getValue

public Value getValue()
               throws java.lang.NullPointerException

Description copied from interface: Expression

Gets evaluated result or null if this expression is not evaluated yet.

Specified by:

getValue in interface Expression

Returns:

evaluated result or null if this expression is not evaluated yet

Throws:

java.lang.NullPointerException

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object