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// PLEASE DO NOT EDIT WITHOUT THE EXPLICIT CONSENT OF THE AUTHOR! \\
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package hlt.language.util;
/**
* This class is a concrete implementation of the abstract class RegExpOne to represent an optional
* regular expression (i.e., zero or one).
*
* @version Last modified on Thu Mar 31 15:55:59 2016 by hak
* @author Hassan Aït-Kaci
* @copyright © Hassan Aït-Kaci
*/
public class RegExpOption extends RegExpOne
{
/**
* Constructs a RegExpOption with the specified
* RegExp.
*/
public RegExpOption (RegExp arg)
{
super(arg);
}
public final int type ()
{
return OPTION_EXP;
}
public final RegExp shallowCopy ()
{
return option(_arg);
}
public final RegExp deepCopy ()
{
return option(_arg.deepCopy());
}
/**
* This computes the normal form of this
* RegExpOption, and sets its _normalForm field to
* it. This normal form is computed according to the following rewrite
* rules.
*
*
*
* -
*
* [OP:E]
*
*
*
* ()?
*
* →
*
*
* ()
*
*
*
*
* -
*
* [OP:O]
*
*
*
* X??
*
* →
*
*
* X?
*
*
*
*
*
* -
*
* [OP:P]
*
*
*
* X+?
*
* →
*
*
* X∗
*
*
*
*
*
* -
*
* [OP:S]
*
*
*
* X∗?
*
* →
*
*
* X∗
*
*
*
*
*
* -
*
* [OP:R0]
*
*
*
* X_0^n?
*
* →
*
*
* X_0^n
*
*
*
*
*
* -
*
* [OP:R1]
*
*
*
* X_1^n?
*
* →
*
*
* X_0^n
*
*
*
*
*
*
*/
public void normalize ()
{
String rule = null;
RegExp arg = arg();
switch (arg.type())
{
case EMPTY_EXP:
rule = "[OP:E] ()? --> ()";
_normalForm = RegExpSymbol.EMPTY;
break;
case OPTION_EXP:
rule = "[OP:O] X?? --> X?";
_normalForm = arg;
break;
case PLUS_EXP:
rule = "[OP:P] X+? --> X*";
_normalForm = star(arg.arg());
break;
case STAR_EXP:
rule = "[OP:S] X*? --> X*";
_normalForm = arg;
break;
case RANGE_EXP:
switch (arg.lower())
{
case 0:
rule = "[OP:R0] X_0^n? --> X_0^n";
_normalForm = arg;
break;
case 1:
rule = "[OP:R1] X_1^n? --> X_0^n";
_normalForm = range(arg.arg(),0,arg.upper());
break;
}
}
traceRule(rule);
checkNormalForm();
}
/**
* Returns a printable form for this RegExpOption.
*/
public final String toString ()
{
if (_arg.isBinary())
return "("+_arg+")?";
return _arg+"?";
}
public final String toNormalString ()
{
if (!inNormalForm())
return _normalForm.toNormalString();
if (_arg.isBinary())
return "("+_arg.toNormalString()+")?";
return _arg.toNormalString()+"?";
}
}