dk.rode.thesis.interpreter
Class EqualExpression

java.lang.Object
  dk.rode.thesis.interpreter.AbstractExpression<E>
      dk.rode.thesis.interpreter.BinaryExpression<Object,Boolean>
          dk.rode.thesis.interpreter.EqualExpression

All Implemented Interfaces:

Expression<Boolean>, NonTerminalExpression<Boolean>, Copyable<Expression<Boolean>>, StrictCopyable<Expression<Boolean>>

@Participant(value="NonTerminalExpression")
public class EqualExpression
extends BinaryExpression<Object,Boolean>
implements NonTerminalExpression<Boolean>

An equal expression can determine if the result of evaluating two expressions is equal or not, regardless of types.

Author:

Gunni Rode / rode.dk

See Also:

CompareExpression, NotExpression, AndExpression, OrExpression

Nested Class Summary

Nested classes/interfaces inherited from interface dk.rode.thesis.interpreter.Expression

Expression.SymbolIdiom

Field Summary

Fields inherited from class dk.rode.thesis.interpreter.BinaryExpression

first, second

Constructor Summary

EqualExpression(EqualExpression expression)
Copy constructor.

EqualExpression(Expression<?> first, Expression<?> second)
Constructor.

Method Summary

String	asSymbol(Context context) Returns x == y, where x is the symbolic representation of the first expression operand and y of the the second.
EqualExpression	copy() Copies this expression.
Boolean	evaluate(Context context) Evaluates this expression and returns the result.
String	name() The stand-alone symbol name for this expression.

Methods inherited from class dk.rode.thesis.interpreter.BinaryExpression

asSymbol, asSymbol, operands, toString

Methods inherited from class dk.rode.thesis.interpreter.AbstractExpression

contains, equals, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface dk.rode.thesis.interpreter.Expression

contains, operands, toString

Constructor Detail

EqualExpression

public EqualExpression(EqualExpression expression)

Copy constructor.

Parameters:

expression - The expression to copy; cannot be null.

Throws:

NullPointerException - If expression is null.

EqualExpression

public EqualExpression(Expression<?> first,
                       Expression<?> second)

Constructor.

Parameters:

first - The first expression operand; cannot be null.

second - The second expression operand; cannot be null.

Throws:

NullPointerException - If either expression is null.

Method Detail

asSymbol

public String asSymbol(Context context)
                throws ExpressionException

Returns x == y, where x is the symbolic representation of the first expression operand and y of the the second.

Specified by:

asSymbol in interface Expression<Boolean>

Parameters:

context - The context to use; never null.

Returns:

The symbolic representation; never null.

Throws:

ExpressionException - If the symbol cannot be generated.

See Also:

Expression.contains(Expression)

copy

public EqualExpression copy()

Description copied from interface: Expression

Copies this expression.

Unlike Expression.asSymbol(Context), copying cannot handle cyclic expression references!

Specified by:

copy in interface Expression<Boolean>

Specified by:

copy in interface Copyable<Expression<Boolean>>

Returns:

A copy of this expression; never null.

evaluate

public Boolean evaluate(Context context)
                 throws ExpressionException

Description copied from interface: Expression

Evaluates this expression and returns the result.

There is no guarantee that the evaluation of this expression will terminate!

Specified by:

evaluate in interface Expression<Boolean>

Parameters:

context - The context to use; cannot be null.

Returns:

The result of the evaluation; never null.

Throws:

ExpressionException - If the evaluation fails.

name

public final String name()

Description copied from interface: Expression

The stand-alone symbol name for this expression.

Specified by:

name in interface Expression<Boolean>

Returns:

equal