C#

Christian Graus wrote:

It also sounds to me like you have a COM component that plays them

internal class Lexer
{
    private TokenList tokens;
    private CharReader reader;

    /// <summary>
    /// Initializes a new instance of the Lexer class with the specified
    /// expression syntax to lex.
    /// </summary>
    /// <param name="expr">An expression to lex.</param>
    internal Lexer(string expr)
        : this(new StringReader(expr))
    {
        // use this
    }

    /// <summary>
    /// Initializes a new instance of the Lexer class with the specified
    /// TextReader to lex.
    /// </summary>
    /// <param name="source">A TextReader to lex.</param>
    internal Lexer(TextReader source)
    {
        // token queue
        tokens = new TokenList();

        // read the file contents
        reader = new CharReader(source);
    }

    /// <summary>
    /// Breaks the input stream onto the tokens list and returns it.
    /// </summary>
    /// <returns>The tokens list.</returns>
    internal TokenList Lex()
    {
        Token token = GetNextToken();
        while(true)
        {
            if(token != null)
                tokens.Add(token);
            else
            {
                tokens.Add(new Token(null, reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.EOF));
                return tokens;
            }

            token = GetNextToken();
        }
    }

    private Token GetNextToken()
    {
        while(!reader.EndOfInput())
        {
            char ch = reader.GetNext();

            // skipping whitespaces
            if(Char.IsWhiteSpace(ch))
            {
                continue;
            }
            switch(ch)
            {
                case '=':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.EQUAL);
                case '+':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.PLUS);
                case '-':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.MINUS);
                case '(':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.LPAREN);
                case ')':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.RPAREN);
                case ',':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.COMMA);
                case '^':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.EXP);
                case '%':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.MODULUS);
                case '!':
                    if (reader.Peek() == '=')
                    {
                        reader.GetNext();   // go past the equal
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.NOTEQUAL);
                    }
                    else
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.NOT);
                case '&':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.PLUSSTRING);
                case '|':
                    if (reader.Peek() == '|')
                    {
                        reader.GetNext();   // go past the '|'
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.OR);
                    }
                    break;
                case '>':
                    if (reader.Peek() == '=')
                    {
                        reader.GetNext();   // go past the equal
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.GREATERTHANOREQUAL);
                    }
                    else
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.GREATERTHAN);
                case '/':
                    if (reader.Peek() == '*')
                    {   // beginning of a comment of form /* a comment */
                        reader.GetNext();   // go past the '*'
                        ReadComment();
                        continue;
                    }
                    else
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.FORWARDSLASH);
                case '<':
                    if (reader.Peek() == '=')
                    {
                        reader.GetNext();   // go past the equal
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.LESSTHANOREQUAL);
                    }
                    else if (reader.Peek() == '>')
                    {
                        reader.GetNext();   // go past the >
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.NOTEQUAL);
                    }
                    else
                        return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.LESSTHAN);
                case '*':
                    return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.STAR);
                case '"':
                case '\'':
                    return ReadQuoted(ch);
                default:
                    break;
            } // end of swith
            if (Char.IsDigit(ch) || ch == '.')
                return ReadNumber(ch);
            else if (Char.IsLetter(ch) || ch == '_')
                return ReadIdentifier(ch);
            else
                return new Token(ch.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.OTHER);
        }
        return null;
    }

    // Reads a decimal number with optional exponentiation
    private Token ReadNumber(char ch)
    {
        int startLine = reader.Line;
        int startCol = reader.Column;
        bool bDecimal = ch == '.'? true: false;
        bool bDecimalType=false;    // found d or D in number
        bool bFloat=false;          // found e or E in number
        char cPeek;

        string number = ch.ToString();
        while(!reader.EndOfInput() )
        {
            cPeek = reader.Peek();
            if (Char.IsWhiteSpace(cPeek))
                break;

            if (Char.IsDigit(cPeek))
                number += reader.GetNext();
            else if (cPeek == 'd' || cPeek == 'D' && !bFloat)
            {
                reader.GetNext();               // skip the 'd'
                bDecimalType = true;
                break;
            }
            else if (cPeek == 'e' || cPeek == 'E' && !bFloat)
            {
                number += reader.GetNext();     // add the 'e'
                cPeek = reader.Peek();
                if (cPeek == '-' || cPeek == '+')
                {
                    number += reader.GetNext();
                    bFloat = true;
                    if (Char.IsDigit(reader.Peek()))
                        continue;
                }
                throw new ParserException("Invalid number constant.");
            }
            else if (!bDecimal && !bFloat && cPeek == '.')  // can't already be decimal or float
            {
                bDecimal = true;
                number += reader.GetNext();
            }
            else
                break;  // another character
        }

        if (number.CompareTo(".") == 0)
            throw new ParserException("'.' should be followed by a number");

        TokenTypes t;
        if (bDecimalType)
            t = TokenTypes.NUMBER;
        else if (bFloat || bDecimal)
            t = TokenTypes.DOUBLE;
        else
            t = TokenTypes.INTEGER;

        return new Token(number, startLine, startCol, reader.Line, reader.Column, t);
    }

    // Reads an identifier:
    //  Must consist of letters, digits, "_".  "!", "." are allowed
    //  but have special meaning that is disambiguated later
    private Token ReadIdentifier(char ch)
    {
        int startLine = reader.Line;
        int startCol = reader.Column;
        char cPeek;

        StringBuilder identifier = new StringBuilder(30);   // initial capacity 30 characters
        identifier.Append(ch.ToString());
        while(!reader.EndOfInput() )
        {
            cPeek = reader.Peek();
            if (Char.IsLetterOrDigit(cPeek) || cPeek == '.' ||
                cPeek == '!' || cPeek == '_')
                identifier.Append(reader.GetNext());
            else
                break;
        }

        string key = identifier.ToString().ToLower();
        if (key == "and" || key == "andalso")   // technically 'and' and 'andalso' mean different things; but we treat the same
            return new Token(identifier.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.AND);
        else if (key == "or" || key == "orelse")    // technically 'or' and 'orelse' mean different things; but we treat the same
            return new Token(identifier.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.OR);
        else if (key == "not")
            return new Token(identifier.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.NOT);
        else if (key == "mod")
            return new Token(identifier.ToString(), reader.Line, reader.Column, reader.Line, reader.Column, TokenTypes.MODULUS);

        // normal identifier
        return new Token(identifier.ToString(), startLine, startCol, reader.Line, reader.Column, TokenTypes.IDENTIFIER);
    }

    // Quoted string like " asdf " or ' asdf '
    private Token ReadQuoted(char ch)
    {
        char qChar = ch;
        int startLine = reader.Line;
        int startCol = reader.Column;
        StringBuilder quoted = new StringBuilder();

        while(!reader.EndOfInput())
        {
            ch = reader.GetNext();
            if (ch == '\\')
            {
                char pChar = reader.Peek();
                if (pChar == qChar)
                    ch = reader.GetNext();          // got one skip escape char
                else if (pChar == 'n')
                {
                    ch = '\n';
                    reader.GetNext();               // skip the character
                }
                else if (pChar == 'r')
                {
                    ch = '\r';
                    reader.GetNext();               // skip the character
                }
            }
            else if (ch == qChar)
                return new Token(quoted.ToString(), startLine, startCol, reader.Line, reader.Column, TokenTypes.QUOTE);

            quoted.Append(ch);
        }
        throw new ParserException("Unterminated string!");
    }

    // Comment string like /* this is a comment */
    private void ReadComment()
    {
        char ch;

        while(!reader.EndOfInput())
        {
            ch = reader.GetNext();
            if (ch == '*' && reader.Peek() == '/')
            {
                reader.GetNext();           // skip past the '/'
                return;
            }
        }
        throw new ParserException("Unterminated comment!");
    }

AndrusM wrote:

Is fyireporting.com parser code best way to implement parser in C# ?

AndrusM wrote:

public virtual EntityType Entity;

abstract class BusinessObject
{
	public abstract EntityType Entity
	{
		get;
		set;
	}
}

AndrusM wrote:

after changing virual to abstract but got error

Error 1 The modifier 'abstract' is not valid on fields. Try using a property instead.

I have seen code using virtual properties in applications.
I'm unable to figure out why this code is not working.

public abstract EntityType Entity;

public class BaseClass
{
    private int someValue = 42;
 
    public virtual int SomeValue
    {
        get
        {
            return someValue;
        }
    }
}

public class DerivedClass : BaseClass
{
    public override int SomeValue
    {
        get
        {
            // Um, do something here...
 
            return base.SomeValue;
        }
    }
}

public abstract class BaseClass
{
    public abstract int SomeValue
    {
        get;
    }
}

public class DerivedClass : BaseClass
{
    private int someValue = 42;
 
    public override int SomeValue
    {
        get
        {
            return someValue;
        }
    }
}

public virtual EntityType Entity { get { return _entityType; } set { _entityType = value; }}

public abstract EntityType Entity { get; set; }

wrote:

what is meant by desktop application?????

Christian Graus wrote:

Please, please, please, STOP asking questions over and over. Answer the people who respond to you, on the same thread