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()
+    {
+    }
+}