elexscannerbase.h

用于词法分析的词法分析器

/*
  $Id: ElexScannerBase.h,v 1.7 1997/03/19 12:16:33 matt Exp $

  Elex scanner base class.

  (c) Matt Phillips 1996.
  */

#ifndef _ELEX_SCAN_BASE_H
#define _ELEX_SCAN_BASE_H

#include <std/string.h>

#include "ElexScannerData.h"

class ElexScannerBase
{
public:

  // Predefined symbol values.
  enum {SymNULL = -1, SymEOF = -2, SymERROR = -3};

  ElexScannerBase (ElexScannerData &d) : data (d), symbol (SymNULL) {}

  virtual ~ElexScannerBase () {}

  // Read next symbol from input.  No effect if at EOF.
  virtual int getNext () = 0;

  // Return the current symbol.
  int getSymbol () const {return symbol;}

  // Return the text matched for current symbol.
  virtual const string &getText () const = 0;
  virtual string &getText () = 0;

  // True if scanner is at end of input.
  int eof () const {return getSymbol () == SymEOF;}

  // Generate an error or warning message.
  virtual void error (const string &message) = 0;
  virtual void warning (const string &message) = 0;

  // Returns true and does a getNext () if current symbol == <sym>,
  // otherwise does nothing and returns false.
  int have (int sym);

protected:

  int symbol;
  ElexScannerData &data;
};

#endif