MyBasic - A Custom-BASIC language interpreter written in C++

// BasicTokenizer.cpp: implementation of the CBasicTokenizer class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "MyBasic.h"
#include "BasicTokenizer.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CBasicTokenizer::CBasicTokenizer()
{
	m_bPushedBack = FALSE;
	m_Keywords.InitHashTable(MAX_KW);
	LowerCaseMode(TRUE);

	InsertKeyword(CString("print"),TT_KW_PRINT);
	InsertKeyword(CString("input"),TT_KW_INPUT);
	InsertKeyword(CString("if"),TT_KW_IF);
	InsertKeyword(CString("then"),TT_KW_THEN);
	InsertKeyword(CString("endif"),TT_KW_ENDIF);
	InsertKeyword(CString("for"),TT_KW_FOR);
	InsertKeyword(CString("next"),TT_KW_NEXT);
	InsertKeyword(CString("to"),TT_KW_TO);
	InsertKeyword(CString("goto"),TT_KW_GOTO);
	InsertKeyword(CString("gosub"),TT_KW_GOSUB);
	InsertKeyword(CString("return"),TT_KW_RETURN);
	InsertKeyword(CString("end"),TT_KW_END);

}

CBasicTokenizer::~CBasicTokenizer()
{

}


void CBasicTokenizer::InsertKeyword(CString &str, int code)
{
	m_Keywords[str] = code;
}

int CBasicTokenizer::NextToken()
{
	if (m_bPushedBack)
	{
		m_bPushedBack = FALSE;
		return m_tType;
	}
	int code;
	int val = CStringTokenizer::NextToken ();
	if (val == TT_WORD && m_Keywords.Lookup(m_sVal,code))
		return m_tType = code;

	if (val == '<')
		if (CStringTokenizer::NextToken () == '=')
			return m_tType = TT_LWE;
		else
		{
			CStringTokenizer::PushBack();
			if (CStringTokenizer::NextToken () == '>')
				return m_tType = TT_NE;
			else
			{
				CStringTokenizer::PushBack();
				return m_tType =val;
			}
		}
	if (val == '>')
		if (CStringTokenizer::NextToken () == '=')
			return m_tType = TT_GTE;
		else
		{
			CStringTokenizer::PushBack();
			return m_tType =val;
		}
	if (val == '=')
		if (CStringTokenizer::NextToken () == '=')
			return m_tType =TT_IS;
		else
			CStringTokenizer::PushBack();
	return m_tType =val;
}

CString CBasicTokenizer::GetStrValue()
{
	CString ret;
	switch (m_tType)
	{
	case TT_EOF:
		ret = "EOF";
		break;
	case TT_EOL:
		ret = "EOL";
		break;
	case TT_WORD:
		ret = m_sVal;
		break;
	case TT_LWE:
		ret = "<=";
		break;
	case TT_GTE:
		ret = ">=";
		break;
	case TT_IS:
		ret = "==";
		break;
	case TT_NE:
		ret = "<>";
		break;
	case TT_STRING:
		ret = m_sVal;
		break;
	case TT_INTEGER:
	case TT_REAL:
		ret.Format("%f",m_dVal);
		break;
	default:
		ret.Format ( "\'%c\'",(char) m_tType) ;
	}
	return ret;
}


void CBasicTokenizer::PushBack()
{
	m_bPushedBack = TRUE;
}