txr: repeat ferrets out Lisp-embedded vars.

Gone is the need for :vars to inform @(repeat)/@(rep) about
variable references buried in Lisp.

* eval.c (expand_with_free_refs): Change to external linkage.

* eval.h (expand_with_free_refs): Declared.

* parser.y (extract_vars): Handle sys:expr forms, which are
embedded Lisp via expand_with_free_refs to uncover their free
variables.

* txr.1: Redocumented this area.

1 files changed, 5 insertions, 1 deletions

diff --git a/parser.y b/parser.y
index d829b4f7..409400f0 100644
--- a/parser.y
+++ b/parser.y
@@ -1519,7 +1519,11 @@ static val extract_vars(val output_spec)
           }
         }
       }
-    } else if (sym != expr_s) {
+    } else if (sym == expr_s) {
+      val expr = second(output_spec);
+      val frefs = expand_with_free_refs(expr, nil, nil);
+      tai = list_collect_nconc(tai, second(frefs));
+    } else {
       for (; output_spec; output_spec = cdr(output_spec))
         tai = list_collect_nconc(tai, extract_vars(car(output_spec)));
     }