private static AstNode parseAdditive(Parser parser)
{
AstNode left = parseMultiplicitive(parser);
while (parser.MatchToken(TokenType.Operation) || parser.MatchToken(TokenType.Identifier, "and") || parser.MatchToken(TokenType.Identifier, "or"))
{
switch ((string)parser.CurrentToken().Value)
{
case "+":
parser.AcceptToken(TokenType.Operation);
left = new BinaryOpNode(BinaryOperation.Addition, left, parseMultiplicitive(parser));
continue;
case "-":
parser.AcceptToken(TokenType.Operation);
left = new BinaryOpNode(BinaryOperation.Subtraction, left, parseMultiplicitive(parser));
continue;
case "and":
parser.AcceptToken(TokenType.Identifier);
left = new BinaryOpNode(BinaryOperation.And, left, parseMultiplicitive(parser));
continue;
case "or":
parser.AcceptToken(TokenType.Identifier);
left = new BinaryOpNode(BinaryOperation.Or, left, parseMultiplicitive(parser));
continue;
default:
break;
}
break;
}
return left;
}
/// <summary>
/// Parse the specified parser.
/// </summary>
/// <param name="parser">Parser.</param>
public static AstNode Parse(Parser parser)
{
if (parser.MatchToken(TokenType.Identifier, "If"))
return ConditionalNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "While"))
return WhileNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "Repeat"))
return RepeatNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "For"))
return ForNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "Disp"))
return DispNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "Input"))
return InputNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "Prompt"))
return PromptNode.Parse(parser);
else if (parser.MatchToken(TokenType.Identifier, "Prgm"))
return PrgmNode.Parse(parser);
else if (parser.AcceptToken(TokenType.Identifier, "Lbl"))
return new LblNode(parser.ExpectToken(TokenType.Identifier).Value);
else if (parser.AcceptToken(TokenType.Identifier, "Goto"))
return new GotoNode(parser.ExpectToken(TokenType.Identifier).Value);
else
return ExpressionNode.Parse(parser);
}
/// <summary>
/// Parse the specified parser.
/// </summary>
/// <param name="parser">Parser.</param>
public static ConditionalNode Parse(Parser parser)
{
parser.ExpectToken(TokenType.Identifier, "If");
AstNode predicate = ExpressionNode.Parse(parser);
AstNode body = StatementNode.Parse(parser);
if (parser.MatchToken(TokenType.Identifier, "Else"))
return new ConditionalNode(predicate, body, StatementNode.Parse(parser));
return new ConditionalNode(predicate, body);
}
private static AstNode parseComparison(Parser parser)
{
AstNode left = parseFunctionCall(parser);
while (parser.MatchToken(TokenType.Comparison))
{
switch ((string)parser.CurrentToken().Value)
{
case "=":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.Equal, left, parseFunctionCall(parser));
continue;
case "!=":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.NotEqual, left, parseFunctionCall(parser));
continue;
case ">":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.GreaterThan, left, parseFunctionCall(parser));
continue;
case "<":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.LessThan, left, parseFunctionCall(parser));
continue;
case ">=":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.GreaterThanOrEqual, left, parseFunctionCall(parser));
continue;
case "<=":
parser.AcceptToken(TokenType.Comparison);
left = new BinaryOpNode(BinaryOperation.LessThanOrEqual, left, parseFunctionCall(parser));
continue;
default:
break;
}
break;
}
return left;
}
private static AstNode parseTerm(Parser parser)
{
if (parser.MatchToken(TokenType.Number))
return new NumberNode(Convert.ToDouble(parser.ExpectToken(TokenType.Number).Value));
else if (parser.AcceptToken(TokenType.Parentheses, "("))
{
AstNode statement = ExpressionNode.Parse(parser);
parser.ExpectToken(TokenType.Parentheses, ")");
return statement;
}
else if (parser.MatchToken(TokenType.Identifier, "Then"))
{
CodeBlockNode block = new CodeBlockNode();
parser.ExpectToken(TokenType.Identifier, "Then");
while (!parser.EndOfStream && !parser.MatchToken(TokenType.Identifier, "EndIf") && !parser.MatchToken(TokenType.Identifier, "Else"))
block.Children.Add(StatementNode.Parse(parser));
if (parser.MatchToken(TokenType.Identifier, "Else"))
return block;
parser.ExpectToken(TokenType.Identifier, "EndIf");
return block;
}
else if (parser.MatchToken(TokenType.Identifier, "Else"))
{
parser.ExpectToken(TokenType.Identifier, "Else");
return StatementNode.Parse(parser);
}
else if (parser.MatchToken(TokenType.Identifier, "Do"))
{
CodeBlockNode block = new CodeBlockNode();
parser.ExpectToken(TokenType.Identifier, "Do");
while (!parser.EndOfStream && !parser.MatchToken(TokenType.Identifier, "End"))
block.Children.Add(StatementNode.Parse(parser));
parser.ExpectToken(TokenType.Identifier, "End");
return block;
}
else if (parser.MatchToken(TokenType.String))
return new StringNode((string)parser.ExpectToken(TokenType.String).Value);
else if (parser.MatchToken(TokenType.Identifier))
return new IdentifierNode((string)parser.ExpectToken(TokenType.Identifier).Value);
else
throw new Exception("Unexpected " + parser.CurrentToken().TokenType + " in Parser: " + parser.CurrentToken().Value + ".");
}
private static AstNode parseMultiplicitive(Parser parser)
{
AstNode left = parseComparison(parser);
while (parser.MatchToken(TokenType.Operation))
{
switch ((string)parser.CurrentToken().Value)
{
case "*":
parser.AcceptToken(TokenType.Operation);
left = new BinaryOpNode(BinaryOperation.Multiplication, left, parseComparison(parser));
continue;
case "/":
parser.AcceptToken(TokenType.Operation);
left = new BinaryOpNode(BinaryOperation.Division, left, parseComparison(parser));
continue;
case "%":
parser.AcceptToken(TokenType.Operation);
left = new BinaryOpNode(BinaryOperation.Modulus, left, parseComparison(parser));
continue;
default:
break;
}
break;
}
return left;
}
private static AstNode parseFunctionCall(Parser parser, AstNode left)
{
if (parser.MatchToken(TokenType.Parentheses, "("))
{
var functionCall = parseFunctionCall(parser, new FunctionCallNode(left, ArgListNode.Parse(parser)));
//parser.ExpectToken(TokenType.Parentheses, ")");
return functionCall;
}
else
return left;
}