Syntax


1   package kawa.lang;
2   import gnu.mapping.*;
3   import gnu.expr.*;
4   import gnu.lists.*;
5   import gnu.text.Printable;
6   
7   /**
8    * Abstract class for "syntax" objects.
9    * Builtins and macros are instances of this class.
10   * @author  Per Bothner
11   */
12  
13  abstract public class Syntax implements Printable, Named
14  {
15    Object   name;
16  
17    public final String   getName()
18    {
19      return name == null ? null
20        : name instanceof Symbol ? ((Symbol) name).getName()
21        : name.toString();
22    }
23    public Object   getSymbol() { return name; }
24  
25    public void setName (Object   name) { this.name = name; }
26    public void setName (String   name) { this.name = name; }
27  
28    public Syntax ()
29    {
30    }
31  
32    public Syntax (Object   name)
33    {
34      setName(name);
35    }
36  
37    /**
38     * Re-write an expression that is an "application" of this Syntax object.
39     * @param obj the arguments to this "application" (i.e. the cdr of
40     * the macro/builtin invokation)
41     * @param tr the Translator that provides context
42     * @return the re-written expression
43     */
44  
45    public Expression rewrite (Object   obj, Translator tr)
46    {
47      throw new InternalError  ("rewrite method not defined");
48    }
49  
50    public Expression rewriteForm (Object   form, Translator tr)
51    {
52      if (form instanceof Pair)
53        return rewriteForm((Pair) form, tr);
54      else
55        return tr.syntaxError("non-list form for "+this);
56    }
57  
58    public Expression rewriteForm (Pair form, Translator tr)
59    {
60      return rewrite(form.cdr, tr);
61    }
62  
63    public void scanForm (Pair st, ScopeExp defs, Translator tr)
64    {
65      boolean ok = scanForDefinitions(st, tr.formStack, defs, tr);
66      if (! ok)
67        tr.formStack.add(new ErrorExp("syntax error expanding "+this));
68    }
69  
70    /** Check if a statement is a definition, for initial pass.
71     * Semi-deprecated - should convert calls to use scanForm.
72     * @param st the statement to check
73     * @param forms where to append the (possibly-modified) statement
74     * @param defs where to add Declarations for found definitions
75     * @param tr the compilation state
76     * @return true on success
77     */
78    public boolean scanForDefinitions (Pair st, java.util.Vector   forms,
79                                      ScopeExp defs, Translator tr)
80    {
81      forms.addElement(st);
82      return true;
83    }
84  
85    public void print (Consumer out)
86    {
87      out.write("#<syntax ");
88      String   name = this.getName();
89      out.write(name == null ? "<unnamed>" : name);
90      out.write('>');
91    }
92  }
93
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