tasks a-s

Task/S-Expressions/Java/s-expressions-1.java

@@ -0,0 +1,111 @@
+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()
+    {
+    }
+}

Task/S-Expressions/Java/s-expressions-2.java

@@ -0,0 +1,29 @@
+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);
+        }
+    }
+}

Task/S-Expressions/Java/s-expressions-3.java

@@ -0,0 +1,17 @@
+package jfkbits;
+
+import jfkbits.LispParser.Expr;
+
+public class Atom implements Expr
+{
+    String name;
+    public String toString()
+    {
+        return name;
+    }
+    public Atom(String text)
+    {
+        name = text;
+    }
+
+}

Task/S-Expressions/Java/s-expressions-4.java

@@ -0,0 +1,20 @@
+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;
+    }
+}

Task/S-Expressions/Java/s-expressions-5.java

@@ -0,0 +1,71 @@
+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);
+    }
+
+}

Task/S-Expressions/Java/s-expressions-6.java

@@ -0,0 +1,47 @@
+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;
+    }
+
+}

Task/S-Expressions/Java/s-expressions-7.java

@@ -0,0 +1,26 @@
+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();
+        }
+    }	
+}