Pattern vars accessed from Lisp now dynamic.

* eval.c (set_dyn_env): Static function becomes external.

* eval.h (set_dyn_env): Declared.

* match.c (eval_with_bindings, eval_progn_with_bindings):
Evaluate Lisp code in null lexical environment. Instead
install the pattern variables as dynamic, so they shadow
global variables. A compatibility check for 121 or earlier
provides the old behavior.

* txr.1: Document scoping rules, and added compatibility
notes.

1 files changed, 29 insertions, 4 deletions

diff --git a/match.c b/match.c
index 45ba7423..8b127a0d 100644
--- a/match.c
+++ b/match.c
@@ -283,20 +283,45 @@ static val eval_with_bindings(val form, val spec,
                               val bindings, val ctx_form)
 {
   val ret;
+
   uw_env_begin;
-  uw_set_match_context(cons(spec, bindings));
-  ret = eval(form, make_env(bindings, nil, nil), ctx_form);
+
+  if (opt_compat && opt_compat <= 121) {
+    uw_set_match_context(cons(spec, bindings));
+    ret = eval(form, make_env(bindings, nil, nil), ctx_form);
+  } else {
+    val saved_de = set_dyn_env(make_env(bindings, nil, nil));
+
+    uw_set_match_context(cons(spec, bindings));
+    ret = eval(form, nil, ctx_form);
+
+    set_dyn_env(saved_de);
+  }
+
   uw_env_end;
   return ret;
 }
 
+
 static val eval_progn_with_bindings(val forms, val spec,
                                     val bindings, val ctx_form)
 {
   val ret;
+
   uw_env_begin;
-  uw_set_match_context(cons(spec, bindings));
-  ret = eval_progn(forms, make_env(bindings, nil, nil), ctx_form);
+
+  if (opt_compat && opt_compat <= 121) {
+    uw_set_match_context(cons(spec, bindings));
+    ret = eval_progn(forms, make_env(bindings, nil, nil), ctx_form);
+  } else {
+    val saved_de = set_dyn_env(make_env(bindings, nil, nil));
+
+    uw_set_match_context(cons(spec, bindings));
+    ret = eval_progn(forms, nil, ctx_form);
+
+    set_dyn_env(saved_de);
+  }
+
   uw_env_end;
   return ret;
 }