Compatibility <= 107 allows redefinition of builtins.

* eval.c (builtin_reject_test): Suppress the diagnostic against
redefinition of built-in macros and operators if the compatibility
is 107 or lower. The rejection appeared in 108.

* txr.1: Document this compatibility behavior.

2 files changed, 8 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index 3800c6ca..c792e99e 100644
--- a/eval.c
+++ b/eval.c
@@ -1469,6 +1469,8 @@ static void builtin_reject_test(val op, val sym, val form)
     if (!bindable(sym)) {
       eval_error(form, lit("~s: cannot bind ~s, which is not a bindable symbol"),
                  is_operator, sym, nao);
+    } else if (opt_compat && opt_compat <= 107) {
+      /* empty */
     } else if (builtin_kind) {
       eval_error(form, lit("~s: cannot bind ~s, which is a built-in ~s"),
                  op, sym, builtin_kind, nao);
diff --git a/txr.1 b/txr.1
index 374e1f31..6cb58443 100644
--- a/txr.1
+++ b/txr.1
@@ -32342,7 +32342,12 @@ Up through \*(TX 107, by accident, there was a function called
 as well as an operator by the same name. The function was renamed to
 .codn flipargs .
 Version 107 compatibility or earlier provides the
-function under the original name also.
+function under the original name also. Also, up until this version,
+\*(TX allowed functions and macros to be defined with the same names
+as built-in operators, and macros. Newer versions reject this as an error.
+Requesting compatibility to 107 or earlier suppresses the rejection,
+though without introducing any requirement that redefinition will work as
+expected.
 
 .IP 105
 Provides the behavior that the