hash: read/print consistency regression.

TXR 188 makes a slight mess of the #H notation. An :eql-based
hash table prints as #H(() ...), but when that notation is
read, it produces an :equal-based hash table. No aspect of
this situation was intended; the intent was that the notation
stays the same as before, and just the hash function changes
to make :equal-based the default. Let's just go with this
and have #H(() ...) denote :equal-based tables.

* hash.c (hash_print_op): Print an :eql-based for eql-based
hash tables, and nothing for equal-based ones. In
compatibility mode with 188 and older, reproduce the old
behavior, rendering equal-based tables with :equal-based and
the absence of a symbol for eql-based.

* txr.1: Updated places that touch on :equal-based and
added compatibility notes.

* tests/009/json.expected: updated, since equal-based hash
tables now print without :equal-based keyword.

1 files changed, 8 insertions, 2 deletions

diff --git a/hash.c b/hash.c
index c5330daf..b0d76175 100644
--- a/hash.c
+++ b/hash.c
@@ -419,10 +419,16 @@ static void hash_print_op(val hash, val out, val pretty, struct strm_ctx *ctx)
 
   put_char(chr('('), out);
 
-  if (h->hash_fun == equal_hash) {
-    obj_print_impl(equal_based_k, out, pretty, ctx);
+  if (opt_compat && opt_compat <= 188) {
+    if (h->hash_fun == equal_hash)
+      obj_print_impl(equal_based_k, out, pretty, ctx);
+    need_space = 1;
+  } else {
+    if (h->hash_fun == eql_hash)
+      obj_print_impl(eql_based_k, out, pretty, ctx);
     need_space = 1;
   }
+
   if (h->flags != hash_weak_none) {
     if (need_space)
       put_char(chr(' '), out);