Source code in the java programming language

package jfkbits;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.StringReader;
import java.util.Iterator;

public class LispTokenizer implements Iterator<Token>
{
    // Instance variables have default access to allow unit tests access.
    StreamTokenizer m_tokenizer;
    IOException m_ioexn;

    /** Constructs a tokenizer that scans input from the given string.
     * @param src A string containing S-expressions.
     */
    public LispTokenizer(String src)
    {
        this(new StringReader(src));
    }

    /** Constructs a tokenizer that scans input from the given Reader.
     * @param r Reader for the character input source
     */
    public LispTokenizer(Reader r)
    {
        if(r == null)
            r = new StringReader("");
        BufferedReader buffrdr = new BufferedReader(r);
        m_tokenizer = new StreamTokenizer(buffrdr);
        m_tokenizer.resetSyntax(); // We don't like the default settings

        m_tokenizer.whitespaceChars(0, ' ');
        m_tokenizer.wordChars(' '+1,255);
        m_tokenizer.ordinaryChar('(');
        m_tokenizer.ordinaryChar(')');
        m_tokenizer.ordinaryChar('\'');
        m_tokenizer.commentChar(';');
        m_tokenizer.quoteChar('"');
    }

    public Token peekToken()
    {	
        if(m_ioexn != null)
            return null;
        try
        {
            m_tokenizer.nextToken();
        }
        catch(IOException e)
        {
            m_ioexn = e;
            return null;
        }
        if(m_tokenizer.ttype == StreamTokenizer.TT_EOF)
            return null;
        Token token = new Token(m_tokenizer);
        m_tokenizer.pushBack();
        return token;
    }

    public boolean hasNext()
    {
        if(m_ioexn != null)
            return false;
        try
        {
            m_tokenizer.nextToken();
        }
        catch(IOException e)
        {
            m_ioexn = e;
            return false;
        }
        if(m_tokenizer.ttype == StreamTokenizer.TT_EOF)
            return false;
        m_tokenizer.pushBack();
        return true;
    }

    /** Return the most recently caught IOException, if any,
     * 
     * @return
     */
    public IOException getIOException()
    {
        return m_ioexn;
    }

    public Token next()
    {
        try
        {
            m_tokenizer.nextToken();
        }
        catch(IOException e)
        {
            m_ioexn = e;
            return null;
        }

        Token token = new Token(m_tokenizer);
        return token;
    }

    public void remove()
    {
    }
}


package jfkbits;
import java.io.StreamTokenizer;

public class Token
{
    public static final int SYMBOL = StreamTokenizer.TT_WORD;
    public int type;
    public String text;
    public int line;

    public Token(StreamTokenizer tzr)
    {
        this.type = tzr.ttype;
        this.text = tzr.sval;
        this.line = tzr.lineno();
    }

    public String toString()
    {
        switch(this.type)
        {
            case SYMBOL:
            case '"':
                return this.text;
            default:
                return String.valueOf((char)this.type);
        }
    }
}


package jfkbits;

import jfkbits.LispParser.Expr;

public class Atom implements Expr
{
    String name;
    public String toString()
    {
        return name;
    }
    public Atom(String text)
    {
        name = text;
    }

}


package jfkbits;

public class StringAtom extends Atom
{
    public String toString()
    {
        // StreamTokenizer hardcodes escaping with \, and doesn't allow \n inside words
        String escaped = name.replace("\\", "\\\\").replace("\n", "\\n").replace("\r", "\\r").replace("\"", "\\\"");
        return "\""+escaped+"\"";
    }

    public StringAtom(String text)
    {
        super(text);
    }
    public String getValue()
    {
        return name;
    }
}


package jfkbits;

import java.util.AbstractCollection;
import java.util.Arrays;
import java.util.Iterator;
import java.util.ArrayList;

import jfkbits.LispParser.Expr;

public class ExprList extends ArrayList<Expr> implements Expr
{
    ExprList parent = null;
    int indent =1;

    public int getIndent()
    {
        if (parent != null)
        {
            return parent.getIndent()+indent;
        }
        else return 0;
    }

    public void setIndent(int indent)
    {
        this.indent = indent;
    }



    public void setParent(ExprList parent)
    {
        this.parent = parent;
    }

    public String toString()
    {
        String indent = "";
        if (parent != null && parent.get(0) != this)
        {
            indent = "\n";
            char[] chars = new char[getIndent()];
            Arrays.fill(chars, ' ');
            indent += new String(chars);		
        }

        String output = indent+"(";
        for(Iterator<Expr> it=this.iterator(); it.hasNext(); ) 
        {
            Expr expr = it.next();
            output += expr.toString();
            if (it.hasNext())
                output += " ";
        }
        output += ")";
        return output;
    }

    @Override
    public synchronized boolean add(Expr e)
    {
        if (e instanceof ExprList)
        {
            ((ExprList) e).setParent(this);
            if (size() != 0 && get(0) instanceof Atom)
                ((ExprList) e).setIndent(2);
        }
        return super.add(e);
    }

}


package jfkbits;


public class LispParser
{
    LispTokenizer tokenizer;

    public LispParser(LispTokenizer input)
    {
        tokenizer=input;
    }

    public class ParseException extends Exception
    {

    }

    public interface Expr
    {
        // abstract parent for Atom and ExprList
    }

    public Expr parseExpr() throws ParseException
    {
        Token token = tokenizer.next();
        switch(token.type)
        {
            case '(': return parseExprList(token);
            case '"': return new StringAtom(token.text);
            default: return new Atom(token.text);
        }
    }


    protected ExprList parseExprList(Token openParen) throws ParseException
    {
        ExprList acc = new ExprList();
        while(tokenizer.peekToken().type != ')')
        {
            Expr element = parseExpr();
            acc.add(element);
        }
        Token closeParen = tokenizer.next();
        return acc;
    }

}


import jfkbits.ExprList;
import jfkbits.LispParser;
import jfkbits.LispParser.ParseException;
import jfkbits.LispTokenizer;

public class LispParserDemo
{
    public static void main(String args[])
    {

        LispTokenizer tzr = new LispTokenizer(
            "((data \"quoted data\" 123 4.5)\n (data (!@# (4.5) \"(more\" \"data)\")))");
        LispParser parser = new LispParser(tzr);

        try
        {
            Expr result = parser.parseExpr();
            System.out.println(result);
        }
        catch (ParseException e1)
        {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }	
}