PatternScope


1   package kawa.lang;
2   import gnu.expr.*;
3   import java.util.Vector  ;
4   
5   /** Bindings from a <code>syntax-case</code>/<code>syntax-rules</code> pattern. */
6   
7   public class PatternScope extends LetExp
8   {
9     PatternScope previousSyntax;
10  
11    /** Currently visible macro pattern names.
12     * For the i'th pattern variable, pattern_names.elementAt(i)
13     * is the name of the variable,  */
14    public Vector   pattern_names;
15  
16    /** Nesting of currently visible macro pattern names.
17     * For the <code>i</code>'th pattern variable,
18     * <code>(int) patternNesting.charAt(i)/2</code> is the nesting (in terms of
19     * number of ellipsis that indicate the variable is repeated).
20     * The low-order bit indicates that if matched value is the <code>car</code>
21     * of the value saved in the <code>vars</code> array. */
22    public StringBuffer   patternNesting;
23  
24    // FIXME - move to Translator?
25    public Declaration matchArray;
26  
27    public PatternScope ()
28    {
29      super(null);
30    }
31  
32    public static PatternScope push (Translator tr)
33    {
34      PatternScope newScope = new PatternScope();
35      PatternScope oldScope = tr.patternScope;
36      newScope.previousSyntax = oldScope;
37      tr.patternScope = newScope;
38      if (oldScope == null)
39        {
40      newScope.pattern_names = new Vector  ();
41      newScope.patternNesting = new StringBuffer  ();
42        }
43      else
44        {
45      newScope.pattern_names = (Vector  ) oldScope.pattern_names.clone();
46      newScope.patternNesting
47        = new StringBuffer  (oldScope.patternNesting.toString());
48        }
49      newScope.outer = tr.currentScope();
50      return newScope;
51    }
52  
53    public static void pop (Translator tr)
54    {
55      tr.patternScope = tr.patternScope.previousSyntax;
56    }
57  
58    /*
59    public void compile (Compilation comp, Target target)
60    {
61      throw new RuntimeException ("internal error - PatternScope.compile called");
62    }
63    */
64  
65  }
66
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