Re: Strange interaction with stream evaluation and define-syntax?

[Per Bothner <per at bothner dot com>]

Stephen Peters wrote:
> I think this might be a bug, but I wanted to make sure that I'm not
> doing something boneheaded.
It's a bug, which prevents a macro from being expanded in the same
compilation unit as it it defined.

I've attached a patch, and also checked it into CVS.  I also
checked in a testcase, based on your bug report.
--
	--Per Bothner
per@bothner.com   http://www.bothner.com/per/
Index: kawa/lang/Macro.java
===================================================================
RCS file: /cvs/kawa/kawa/kawa/lang/Macro.java,v
retrieving revision 1.16
diff -u -r1.16 Macro.java
--- kawa/lang/Macro.java	29 May 2002 06:20:38 -0000	1.16
+++ kawa/lang/Macro.java	23 Aug 2002 06:34:35 -0000
@@ -7,7 +7,7 @@
 
 public class Macro extends Syntax implements Printable, Externalizable
 {
-  public Expression expander;
+  public Object expander;
 
   java.util.Vector capturedIdentifiers;
 
@@ -21,11 +21,6 @@
    * The binding (if any) for templateIdentifiers[i] is capturedDeclarations[i]. */
   Object[] capturedDeclarations;
 
-  public Expression getExpander()
-  {
-    return expander;
-  }
-
   public static Macro make (Declaration decl)
   {
     Macro mac = new Macro(decl.getName());
@@ -142,8 +137,29 @@
   {
     try
       {
-        Procedure pr
-	  = (Procedure) getExpander().eval(tr.getGlobalEnvironment());
+	Procedure pr;
+	Object exp = expander;
+	if (exp instanceof Procedure)
+	  pr = (Procedure) exp;
+	else
+	  {
+	    if (! (exp instanceof Expression))
+	      {
+		Macro savedMacro = tr.currentMacroDefinition;
+		tr.currentMacroDefinition = this;
+		try
+		  {
+		    exp = tr.rewrite(exp);
+		    expander = exp;
+		  }
+		finally
+		  {
+		    tr.currentMacroDefinition = savedMacro;
+		  }
+	      }
+	    pr = (Procedure)
+	      ((Expression) exp).eval(tr.getGlobalEnvironment());
+	  }
         SyntaxForm sform = new SyntaxForm();
         sform.form = form;
         sform.tr = tr;
Index: kawa/standard/define_syntax.java
===================================================================
RCS file: /cvs/kawa/kawa/kawa/standard/define_syntax.java,v
retrieving revision 1.20
diff -u -r1.20 define_syntax.java
--- kawa/standard/define_syntax.java	29 May 2002 06:20:39 -0000	1.20
+++ kawa/standard/define_syntax.java	23 Aug 2002 06:34:35 -0000
@@ -3,6 +3,7 @@
 import gnu.expr.*;
 import gnu.bytecode.ClassType;
 import gnu.bytecode.Method;
+import gnu.mapping.Procedure;
 import gnu.lists.*;
 
 public class define_syntax extends Syntax
@@ -30,27 +31,36 @@
     if (! (pair.cdr instanceof Pair))
       return tr.syntaxError("Missing transformation for "+form.car);
     pair = (Pair) pair.cdr;
-    Macro savedMacro = tr.currentMacroDefinition;
-    tr.currentMacroDefinition = macro;
-    Expression rule = tr.rewrite(pair.car);
-    tr.currentMacroDefinition = savedMacro;
-    macro.expander = rule;
+    Object expander = macro.expander;;
+    if (! (expander instanceof Procedure)
+	&& ! (expander instanceof Expression))
+      {
+	Macro savedMacro = tr.currentMacroDefinition;
+	tr.currentMacroDefinition = macro;
+	expander = tr.rewrite(macro.expander);
+	tr.currentMacroDefinition = savedMacro;
+	macro.expander = expander;
+      }
     if (! (decl.context instanceof ModuleExp))
       {
 	return QuoteExp.voidExp;
       }
     else
       {
-	if (! (rule instanceof QuoteExp)
-	    || ! (((QuoteExp) rule).getValue() instanceof java.io.Externalizable))
+	if (expander instanceof QuoteExp)
+	  expander = ((QuoteExp) expander).getValue();
+	Expression rule;
+	if (expander instanceof Procedure
+	    && expander instanceof java.io.Externalizable)
+	  rule = new QuoteExp(macro);
+	else
 	  {
 	    Expression args[] = new Expression[2];
 	    args[0] = new QuoteExp(name);
-	    args[1] = rule;
+	    args[1] = expander instanceof Expression ? (Expression) expander
+	      : new QuoteExp (expander);
 	    rule = new ApplyExp(new PrimProcedure(makeMethod), args);
 	  }
-	else
-	  rule = new QuoteExp(macro);
         SetExp result = new SetExp (decl, rule);
         result.setDefining (true);
         return result;
@@ -76,7 +86,7 @@
 
     Declaration decl = defs.getDefine(name, 'w', tr);
     Macro macro = Macro.make(decl);
-
+    macro.expander = p.car;
     p = tr.makePair(st, this, new Pair(decl, p));
     forms.addElement (p);