private Expression ParseExpression()
{
Expression parsedExpression;
if (currentToken == listTokens.Count)
{
ExceptionHandler("expected expression, got EOF");
}
if (listTokens[currentToken] is StringBuilder)
{
string value = ((StringBuilder)listTokens[currentToken++]).ToString();
AlphaNumericValue _AlphaNumericValue = new AlphaNumericValue();
_AlphaNumericValue.Value = value;
parsedExpression = _AlphaNumericValue;
}
else if (listTokens[currentToken] is int)
{
int intValue = (int)listTokens[currentToken++];
NumericValue _NumericValue = new NumericValue();
_NumericValue.Value = intValue;
parsedExpression = _NumericValue;
}
else if (listTokens[currentToken] is string)
{
string identifier = (string)listTokens[currentToken++];
Identifier _Identifier = new Identifier();
_Identifier.IdentifierName = identifier;
parsedExpression = _Identifier;
}
else
{
ExceptionHandler("expected string literal, int literal, or variable");
return(null);
}
//if (index < listTokens.Count && listTokens[index] != Scanner.Terminator && listTokens[index].GetType() != typeof(StringBuilder))
if (listTokens[currentToken].ToString() != Lexer.Tokens.Terminator.ToString())
{
if (listTokens[currentToken].ToString() == Lexer.Tokens.Add.ToString() || listTokens[currentToken].ToString() == Lexer.Tokens.Subtract.ToString() ||
listTokens[currentToken].ToString() == Lexer.Tokens.Multiply.ToString() || listTokens[currentToken].ToString() == Lexer.Tokens.Divide.ToString())
{
ArithmaticExpression arithmaticExpression = new ArithmaticExpression();
arithmaticExpression.Left = parsedExpression;
if (listTokens[currentToken].ToString() == Lexer.Tokens.Add.ToString())
{
arithmaticExpression.Operand = ArithmaticOperands.Add;
}
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Subtract.ToString())
{
arithmaticExpression.Operand = ArithmaticOperands.Subtract;
}
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Multiply.ToString())
{
arithmaticExpression.Operand = ArithmaticOperands.Multiply;
}
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Divide.ToString())
{
arithmaticExpression.Operand = ArithmaticOperands.Division;
}
currentToken++;
arithmaticExpression.Right = ParseExpression();
parsedExpression = arithmaticExpression;
}
}
return(parsedExpression);
}
public void GenerateExpressionMethod(Expression _expression, System.Type expressionType)
{
System.Type typeOfExpression;
if (_expression is AlphaNumericValue)
{
typeOfExpression = typeof(string);
_ILMethod.Emit(OpCodes.Ldstr, ((AlphaNumericValue)_expression).Value);
}
else if (_expression is NumericValue)
{
typeOfExpression = typeof(int);
_ILMethod.Emit(OpCodes.Ldc_I4, ((NumericValue)_expression).Value);
}
else if (_expression is ArithmaticExpression)
{
typeOfExpression = GetExpressionTypeMethod(_expression);
ArithmaticExpression arithmaticExpression = (ArithmaticExpression)_expression;
GenerateExpressionMethod(arithmaticExpression.Left, GetExpressionTypeMethod(arithmaticExpression.Left));
GenerateExpressionMethod(arithmaticExpression.Right, GetExpressionTypeMethod(arithmaticExpression.Right));
if (arithmaticExpression.Operand == ArithmaticOperands.Add)
{
_ILMethod.Emit(OpCodes.Add);
}
else if (arithmaticExpression.Operand == ArithmaticOperands.Subtract)
{
_ILMethod.Emit(OpCodes.Sub);
}
else if (arithmaticExpression.Operand == ArithmaticOperands.Multiply)
{
_ILMethod.Emit(OpCodes.Mul);
}
else if (arithmaticExpression.Operand == ArithmaticOperands.Division)
{
_ILMethod.Emit(OpCodes.Div);
}
}
else if (_expression is Identifier)
{
string identifier = ((Identifier)_expression).IdentifierName;
typeOfExpression = GetExpressionTypeMethod(_expression);
if (!tblIdentifier.ContainsKey(identifier) && !tblArguments.ContainsKey(identifier))
{
ExceptionHandler("undeclared variable '" + identifier + "'");
}
if (tblIdentifier.ContainsKey(identifier))
{
_ILMethod.Emit(OpCodes.Ldloc, tblIdentifier[identifier]);
}
else
{
_ILMethod.Emit(OpCodes.Ldloc, tblArguments[identifier]);
}
}
else
{
ExceptionHandler("can't generate " + _expression.GetType().Name);
typeOfExpression = null;
}
if (typeOfExpression != expressionType)
{
if (typeOfExpression == typeof(int) &&
expressionType == typeof(string))
{
_ILMethod.Emit(OpCodes.Box, typeof(int));
_ILMethod.Emit(OpCodes.Callvirt, typeof(object).GetMethod("ToString"));
}
else
{
ExceptionHandler("can't convert " + typeOfExpression.Name + " to " + expressionType.Name);
}
}
}
