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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 a "starred"
* regular expression (i.e., zero or more).
*
* @version Last modified on Thu Mar 31 15:56:44 2016 by hak
* @author Hassan Aït-Kaci
* @copyright © Hassan Aït-Kaci
*/
public class RegExpStar extends RegExpOne
{
/**
* Constructs a RegExpStar with the specified
* RegExp.
*/
public RegExpStar (RegExp arg)
{
super(arg);
}
public final RegExp shallowCopy ()
{
return star(_arg);
}
public final RegExp deepCopy ()
{
return star(_arg.deepCopy());
}
public final int type ()
{
return STAR_EXP;
}
/**
* This returns this RegExpStar's
* normal form according to the following rewrite rules:
*
*
*
* -
*
* [ST:E]
*
*
*
* ()\*
*
* →
*
*
* ()
*
*
*
*
-
*
* [ST:O]
*
*
*
* X?\*
*
* →
*
*
* X\*
*
*
*
*
-
*
* [ST:P]
*
*
*
* X+\*
*
* →
*
*
* X\*
*
*
*
*
-
*
* [ST:S]
*
*
*
* X\*\*
*
* →
*
*
* X\*
*
*
*
*
*
* Note that there are no rules for X^n\* nor
* X_n^m\* since such forms cannot be further normalized.
*/
public void normalize ()
{
String rule = null;
RegExp arg = arg();
switch (arg.type())
{
case EMPTY_EXP:
rule = "[ST:E] ()* --> ()";
_normalForm = RegExpSymbol.EMPTY;
break;
case OPTION_EXP:
rule = "[ST:O] X?* --> X*";
_normalForm = star(arg.arg());
break;
case PLUS_EXP:
rule = "[ST:P] X+* --> X*";
_normalForm = star(arg.arg());
break;
case STAR_EXP:
rule = "[ST:S] X** --> X*";
_normalForm = arg;
break;
}
traceRule(rule);
checkNormalForm();
}
/**
* Returns a printable form for this RegExpStar.
*/
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()+"*";
}
}