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//
// SimpleQueryParser.cc
//
// SimpleQueryParser: (abstract) a family of parsers that generate queries
// for strings with the syntax (word|phrase){(word|phrase)}
// combining them in a single operator.
// The operator to apply is tbd by concrete classes.
//
// Part of the ht://Dig package <https://htdig.sourceforge.net/>
// Copyright (c) 1995-2004 The ht://Dig Group
// For copyright details, see the file COPYING in your distribution
// or the GNU Library General Public License (LGPL) version 2 or later
// <http://www.gnu.org/copyleft/lgpl.html>
//
// $Id: SimpleQueryParser.cc,v 1.4 2004/05/28 13:15:24 lha Exp $
//
#include "SimpleQueryParser.h"
#include "OperatorQuery.h"
//
// expr == term { term }
//
Query *
SimpleQueryParser::ParseExpression()
{
Query *result = 0;
Query *term = ParseTerm();
if(term)
{
if(token.IsEnd())
{
result = term;
}
else
{
result = MakeQuery();
result->Add(term);
while(!token.IsEnd())
{
term = ParseTerm();
if(term)
{
result->Add(term);
}
}
}
}
if(!term)
{
delete result;
result = 0;
}
return result;
}
//
// term == word | '"' phrase '"'
//
Query *
SimpleQueryParser::ParseTerm()
{
Query *result = 0;
if(token.IsQuote())
{
token.Next();
result = ParsePhrase();
if(result)
{
if(token.IsQuote())
{
token.Next();
}
else
{
Expected("closing \"");
delete result;
result = 0;
}
}
}
else if(token.IsWord())
{
// don't advance token here!
result = ParseWord();
}
else
{
Expected("a word or a quoted phrase");
}
return result;
}
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