Values


1   package gnu.mapping;
2   import java.io.*;
3   import gnu.lists.*;
4   import gnu.text.Printable;
5   
6   /** Encapsulate multiple values in a single object.
7    * In Scheme and Lisp mainly used to return multiple values from a function.
8    */
9   
10  public class Values extends TreeList implements Printable, Externalizable
11  {
12    public static final Object  [] noArgs = new Object  [0];
13  
14    public static final Values empty = new Values(noArgs);
15  
16    public Values ()
17    {
18    }
19  
20    /** Constructor.
21     * @param values the values to encapulate
22     */
23    public Values (Object  [] values)
24    {
25      for (int i = 0;  i < values.length;  i++)
26        writeObject(values[i]);
27    }
28  
29    /** Get the values encapsulated. */
30    // Used by CallContext.writeValue, call_with_values.apply(CallContext) FIXME
31    public Object  [] getValues ()
32    {
33      return isEmpty() ? noArgs : toArray();
34    }
35  
36    public static Object   values$V(Object  [] vals)
37    {
38      return make(vals);
39    }
40  
41    public static Values make ()
42    {
43      return new Values();
44    }
45  
46    public static Object   make (Object  [] vals)
47    {
48      if (vals.length == 1)
49        return vals[0];
50      else if (vals.length == 0)
51        return empty;
52      else
53        return new Values(vals);    
54    }
55  
56    public static Object   make (Sequence seq)
57    {
58      int count = seq.size();
59      if (count == 0)
60        return empty;
61      if (count == 1)
62        return seq.get(0);
63      Values vals = new Values();
64      java.util.Enumeration   it = seq.elements();
65      while (it.hasMoreElements())
66        vals.writeObject(it.nextElement());
67      return vals;
68    }
69  
70    public static Object   make (TreeList list)
71    {
72      return make(list, 0, list.data.length);
73    }
74  
75    public static Object   make (TreeList list, int startPosition, int endPosition)
76    {
77      int next;
78      if (startPosition == endPosition
79      || (next = list.nextDataIndex(startPosition)) <= 0)
80        return empty;
81      if (next == endPosition || list.nextDataIndex(next) < 0)
82        return list.getPosNext(startPosition << 1); // Singleton value
83      Values vals = new Values();
84      list.consumeIRange(startPosition, endPosition, vals);
85      return vals;
86    }
87  
88    /** If a simple value, return that value.
89     * Also, if no values, return empty.
90     */
91    public final Object   canonicalize ()
92    {
93      if (gapEnd == data.length)
94        {
95      if (gapStart == 0)
96        return empty;
97      if (nextDataIndex(0) == gapStart) // Singleton value.
98        return getPosNext(0);
99        }
100     return this;
101   }
102 
103   /** Apply a Procedure with these values as the arguments. */
104   public Object   call_with (Procedure proc) throws Throwable  
105   {
106     return proc.applyN (toArray());
107   }
108 
109   public void print (Consumer out)
110   {
111     if (this == empty)
112       {
113     out.write("#!void");
114     return;
115       }
116     Object  [] vals = toArray();  // FIXME!
117     int size = vals.length;
118     boolean readable = true;  // FIXME
119     if (readable)
120       out.write("#<values");
121     for (int i = 0;;)
122       {
123         int next = nextDataIndex(i);
124         if (next < 0)
125           break;
126     out.write(' ');
127         if (i >= gapEnd)
128           i -= gapEnd - gapStart;
129         Object   val = getPosNext(i << 1);
130         if (val instanceof Printable)
131           ((Printable) val).print(out);
132         else
133           out.writeObject(val);
134         i = next;
135       }
136     if (readable)
137       out.write('>');
138   }
139 
140   /**
141    * @serialData Write the length (using writeInt), followed by
142    *   the values in order (written using writeObject).
143    */
144   public void writeExternal(ObjectOutput out) throws IOException
145   {
146     Object  [] vals = toArray();  // FIXME
147     int len = vals.length;
148     out.writeInt(len);
149     for (int i = 0;  i < len;  i++)
150       out.writeObject(vals[i]);
151   }
152 
153   public void readExternal(ObjectInput in)
154     throws IOException, ClassNotFoundException  
155   {
156     int len = in.readInt();
157     for (int i = 0;  i < len;  i++)
158       writeObject(in.readObject());
159   }
160 
161   public Object   readResolve() throws ObjectStreamException
162   {
163     return isEmpty() ? empty : this;
164   }
165 
166   /** Helper method called by code using a SeriesTarget.
167    * The compiled code iterates through zero or more values.
168    * Return the index of the next value, or -1 if currently at eof.
169    * A non-Values object is treated as a singleton value,
170    * so in that case there is no next value.
171    */
172   public static int nextIndex(Object   values, int curIndex)
173   {
174     if (values instanceof Values)
175       return ((Values) values).nextDataIndex(curIndex);
176     else
177       return curIndex == 0 ? 1 : -1;
178   }
179 
180   /** Helper method called by code using a SeriesTarget.
181    * The compiled code iterates through zero or more values.
182    * Extract the object referenced by the curIndex.
183    * A non-Values object is treated as a singleton value.
184    */
185   public static Object   nextValue(Object   values, int curIndex)
186   {
187     if (values instanceof Values)
188       {
189     Values v = (Values) values;
190     if (curIndex >= v.gapEnd)
191       curIndex -= v.gapEnd - v.gapStart;
192     return ((Values) values).getPosNext(curIndex << 1);
193       }
194     else
195       return values;
196   }
197 
198   public static void writeValues(Object   value, Consumer out)
199   {
200     if (value instanceof Values)
201       {
202     ((Values) value).consume(out);
203     /*
204     Object[] values = ((Values) value).getValues();
205     for (int i = 0;  i < values.length;  i++)
206       writeValues(values[i], out);
207     */
208       }
209     /*
210     else if (value instanceof Consumable)
211       {
212     ((Consumable) value).consume(out);
213       }
214     */
215     else
216       out.writeObject(value);
217   }
218 
219   public static int countValues (Object   value)
220   {
221     return value instanceof Values ? ((Values) value).size() : 1;
222   }
223 }
224
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags