Syntax ParseFactor()
{
var token = Read();
switch (token.Type)
{
case TokenType.Identifier:
if (Match(TokenType.OpenParenthese))
{
Read();
List <Syntax> arguments = new List <Syntax>();
while (!Match(TokenType.CloseParenthese))
{
var argument = ParseBinaryExpression(0);
arguments.Add(argument);
if (!Match(TokenType.CloseParenthese))
{
Expect(TokenType.Comma);
}
}
Expect(TokenType.CloseParenthese);
return(new FunctionExpression(token.Contents, arguments, token));
}
else
{
return(new IdentifierExpression(token.Contents, token));
}
case TokenType.Field:
return(new FieldExpression(token.Contents, token));
case TokenType.OpenParenthese:
Syntax parenthesizedExpression = ParseBinaryExpression(0);
Expect(TokenType.CloseParenthese);
return(parenthesizedExpression);
case TokenType.DecimalLiteral:
case TokenType.BooleanLiteral:
case TokenType.StringLiteral:
case TokenType.DateTimeLiteral:
case TokenType.Null:
return(new LiteralExpression(token.Contents, token));
default:
throw ScriptError.UnexpectedToken(token, token.Contents);
}
}
public Token Expect(params TokenType[] types)
{
if (Index >= Tokens.Count)
{
throw ScriptError.UnexpectedEOF(null);
}
foreach (var type in types)
{
if (Tokens[Index].Type == type)
{
var token = Tokens[Index];
Index++;
return(token);
}
}
throw ScriptError.UnexpectedToken(Tokens[Index], Tokens[Index].Contents);
}
