org.expasy.jpl.commons.base.cond
Class ConditionInterpreter<T>

java.lang.Object
  org.expasy.jpl.commons.base.cond.ConditionInterpreter<T>

All Implemented Interfaces:

Interpreter<Condition<T>>

public final class ConditionInterpreter<T>
extends Object
implements Interpreter<Condition<T>>

ConditionInterpreter translates condition type expressions into Condition. It helps building complex ConditionImpls.

Expressions are represented as an expression tree. [conditional] Expression trees represent code in a tree-like data structure, where each node is a expression over condition.

A complex conditional expression is an expression of simple condition operands (defined internally as variable (CVAR)) and classic unary (OR) and binary operators (AND, OR). Here is the grammar below:

EXPR := COND | NOT? EXPR
COND := CVAR BOP COND
CVAR := \w+
BOP := AND | OR
NOT := '!'
AND := '&'
OR := '|'

How to create a complex condition ?

1. register simple conditions in engine as variables (CVAR).
2. compile engine with a given string expression of defined variables (CVAR) and logical operators (NOT, AND and OR).
3. get and test the condition as a simple condition Condition.

Example:

 ConditionInterpreter<Double> interpreter =
        ConditionInterpreter.newInstance();
 
 engine.register("c1", new ConditionImpl.Builder<Double, Double>(0.)
   .operator(OperatorGreaterThan.newInstance()).build());

 
 engine.register("c2", new ConditionImpl.Builder<Double, Double>(10.)
   .operator(OperatorLowerThan.newInstance()).build());

 
 Condition<Double> condition = interpreter.translate("c1 & c2");
 
 Assert.assertTrue(condition.evaluate(4.));
 Assert.assertFalse(condition.evaluate(14.));
 

Version:

1.0

Author:

nikitin

See Also:

ConditionImpl

Method Summary

Condition<T>	getCondition(String name) Get the condition given its name.
String	getNextConditionName()
int	getNumOfCondition()
static <T> ConditionInterpreter<T>	newInstance()
ConditionInterpreter<T>	register(Condition<T> condition) Add anonymous condition instance in the condition table.
ConditionInterpreter<T>	register(String condition) Add anonymous condition.
ConditionInterpreter<T>	register(String conditionName, Condition<T> condition) Add a named condition in the condition table.
ConditionInterpreter<T>	register(String conditionName, String condition)
void	removeAllConditions() Remove all conditions.
Condition<T>	removeCondition(String name) Remove the condition.
void	traceInternalConditions() Display the internal content of defined conditions variables.
Condition<T>	translate(String expression) Parse expression and return a tree conditional expression.

Methods inherited from class java.lang.Object

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

Method Detail

newInstance

public static <T> ConditionInterpreter<T> newInstance()

register

public ConditionInterpreter<T> register(String conditionName,
                                        Condition<T> condition)

Add a named condition in the condition table.

Parameters:

conditionName - the condition name.

condition - the condition instance.

register

public ConditionInterpreter<T> register(Condition<T> condition)

Add anonymous condition instance in the condition table.

Do not forget to get

Parameters:

condition - the condition instance.

register

public ConditionInterpreter<T> register(String conditionName,
                                        String condition)
                                 throws OperatorManager.InvalidOperatorException

Throws:

OperatorManager.InvalidOperatorException

register

public ConditionInterpreter<T> register(String condition)
                                 throws OperatorManager.InvalidOperatorException

Add anonymous condition.

Parameters:

condition - the string format condition.

Returns:

the engine.

Throws:

OperatorManager.InvalidOperatorException

getNextConditionName

public String getNextConditionName()

Returns:

the next generated condition name.

removeCondition

public Condition<T> removeCondition(String name)

Remove the condition.

Parameters:

name - the condition name.

Returns:

the removed condition.

removeAllConditions

public void removeAllConditions()

Remove all conditions.

getCondition

public Condition<T> getCondition(String name)

Get the condition given its name.

Parameters:

name - the condition name.

Returns:

the fetched condition.

getNumOfCondition

public int getNumOfCondition()

Returns:

the number of stored condition.

traceInternalConditions

public void traceInternalConditions()

Display the internal content of defined conditions variables.

translate

public Condition<T> translate(String expression)
                       throws ParseException

Parse expression and return a tree conditional expression.

Specified by:

translate in interface Interpreter<Condition<T>>

Parameters:

expression - the expression to evaluate.

Returns:

a tree expression of conditions.

Throws:

ParseException - if invalid expression.