syntax: read and print [. x] and [. @x].

* lib.c (obj_print_impl): Handle (dwim . atom) syntax
by printing [. atom].  Note that (dwim . @var)
and (dwim . @(expr)) already print as [. @var]
and [. @(expr)]; this is not new. But none of these
forms are supported by reading without the
accompanying change to the parser.

* parser.y (dwim): Handle the [. expr] and [ . expr]
syntax, so that forms like [. a] and [. @a] have
print-read consistency. The motivation is to be
able to [. @args] in pattern matching to match a
DWIM forms; I tried that and was surprised to have it
blow up in my face.

* tests/012/readprint.tl: New test file. Future
printer/parser changes will be tested here. Historically,
changes to the syntax have not been consistently
unit-tested.

* y.tab.c.shipped: Regenerated.

1 files changed, 7 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index fbb5d9e8..9e220f10 100644
--- a/lib.c
+++ b/lib.c
@@ -14099,8 +14099,14 @@ val obj_print_impl(val obj, val out, val pretty, struct strm_ctx *ctx)
         cnum max_len = ctx->strm->max_length;
         cnum max_count = max_len;
 
-        if (sym == dwim_s && have_args) {
+        if (sym == dwim_s) {
           put_char(chr('['), out);
+          if (!have_args) {
+            put_string(lit(". "), out);
+            obj_print_impl(args, out, pretty, ctx);
+            put_char(chr(']'), out);
+            break;
+          }
           obj = args;
           closepar = chr(']');
         } else {