expander: new rule for macro-produced function calls

* eval.c (do_expand): When a function call's arguments are
expanded and produce a transformation, then if that function
call had been produced by a macro, the transformed function
call is tried again as a macro. This is necessary because
TXR Lisp allows a symbol to be both a function and macro.
When a macro-produced function call's arguments are expanded,
the macro version of that function may, as a result of the
argument transformations, have more opportunities for expansion.

* txr.1: New section outlining how macro expansion generally
works, with a special focus on this unusual new rule.

1 files changed, 6 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index f6268344..b8a611d2 100644
--- a/eval.c
+++ b/eval.c
@@ -5255,7 +5255,12 @@ again:
         return form_ex;
       }
 
-      return rlcp(cons(insym_ex, args_ex), form);
+      form = rlcp(cons(insym_ex, args_ex), form);
+      if (macro) {
+        macro = nil;
+        goto again;
+      }
+      return form;
     }
     abort();
   }