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Jadex Rules is a small lightweight rule engine, which currently
employs the well-known Rete algorithm for highly efficient rule
matching. Jadex rules is therefore similar to other rule engines
like JESS and Drools. Despite the similarities there are also
important differences between these systems:
* Jadex Rules is very small and
intended to be used as component
of other software. Even though rules can be specified in a Java
dialect as well as (a small variation of) the CLIPS language
its primary usage is on the API level. Jadex Rules is currently
the core component of the Jadex BDI reasoning engine.
* Jadex Rules cleanly separates between state and rule representation.
This allows the state implementation as well as the matcher to be
flexibly exchanged. Some experiments have e.g. been conducted with
a Jena representation. Regarding the matcher, it is planned to
support also the Treat algorithm, which has a lower memory footprint
than Rete.
* Jadex Rules pays close attention to rule debugging. The state as
well as the rete engine can be observed at runtime. The rule debugger
provides functionalities to execute a rule program stepwise and also
use rule breakpoints to stop the execution at those points.
package jadex.rules.parser.conditions.javagrammar;
import jadex.rules.rulesystem.rules.Variable;
/**
* An unary operation operates on one value.
*/
public class UnaryExpression extends Expression
{
//-------- constants --------
/** The not operator "!". */
public static final String OPERATOR_NOT = "!";
/** The (unary) minus operator "-". */
// unary plus is ignored by parser.
public static final String OPERATOR_MINUS = "-";
/** The bitwise not operator "~". */
public static final String OPERATOR_BNOT = "~";
//-------- attributes --------
/** The value expression. */
protected Expression value;
/** The operator. */
protected String operator;
//-------- constructors --------
/**
* Create a new unary operation.
*/
public UnaryExpression(Expression value, String operator)
{
this.value = value;
this.operator = operator;
}
//-------- methods --------
/**
* Test if a variable is contained in the expression.
* @param var The variable.
* @return True, when the variable is contained.
*/
public boolean containsVariable(Variable var)
{
return value.containsVariable(var);
}
/**
* Get the value.
*/
public Expression getValue()
{
return this.value;
}
/**
* Get the operator.
*/
public Object getOperator()
{
return this.operator;
}
/**
* Get a string representation of this expression.
*/
public String toString()
{
StringBuffer ret = new StringBuffer();
ret.append(getOperator());
ret.append("(");
ret.append(getValue().toString());
ret.append(")");
return ret.toString();
}
/**
* Test if this expression is equal to some object.
*/
public boolean equals(Object o)
{
return o instanceof UnaryExpression
&& ((UnaryExpression)o).getValue().equals(getValue())
&& ((UnaryExpression)o).getOperator().equals(getOperator());
}
/**
* Get the hash code of this expression.
*/
public int hashCode()
{
int ret = 31 + getValue().hashCode();
ret = 31*ret + getOperator().hashCode();
return ret;
}
}