New @(push) directive.

@(push) is like @(output), but feeds back into input.
Use carefully.

* parser.y (PUSH): New token.
(output_push): New nonterminal symbol.
(output_clause): Handle OUTPUT or PUSH via output_push.
Some logic moved to output_helper.
(output_helper): New function. Transforms both @(output)
and @(push) directives. Checks both for valid keywords;
push has only :filter.

* parser.l (grammar): Recognize @(push similarly to other
directives.

* lib.[ch] (push_s): New symbol variable.

* match.c (v_output_keys): Internal linkage changes to external.
(v_push): New function.
(v_parallel): We must fix the max_line algorithm not to
use an initial value of zero, because lines can go negative
thanks to @(push). We end up rejecting the pushed data.
(v_collect): We can no longer assert that the data line
number doesn't retreat.

(dir_tables_init): Register push directive in table of
vertical directives.

* match.h (append_k, continue_k, finish_k): Existing symbol
variables declared.
(v_output_keys): Declared.

* y.tab.c.shipped,
* y.tab.h.shipped,
* lex.yy.c.shipped: Updated.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index c52f9575..422cb693 100644
--- a/lib.c
+++ b/lib.c
@@ -110,7 +110,7 @@ val zeroplus_s, optional_s, compl_s, compound_s;
 val or_s, and_s, quasi_s, quasilist_s;
 val skip_s, trailer_s, block_s, next_s, freeform_s, fail_s, accept_s;
 val all_s, some_s, none_s, maybe_s, cases_s, collect_s, until_s, coll_s;
-val define_s, output_s, single_s, first_s, last_s, empty_s;
+val define_s, output_s, push_s, single_s, first_s, last_s, empty_s;
 val repeat_s, rep_s, flatten_s, forget_s;
 val local_s, merge_s, bind_s, rebind_s, cat_s;
 val try_s, catch_s, finally_s, throw_s, defex_s, deffilter_s;
@@ -13835,6 +13835,7 @@ static void obj_init(void)
   coll_s = intern(lit("coll"), user_package);
   define_s = intern(lit("define"), user_package);
   output_s = intern(lit("output"), user_package);
+  push_s = intern(lit("push"), user_package);
   single_s = intern(lit("single"), user_package);
   first_s = intern(lit("first"), user_package);
   last_s = intern(lit("last"), user_package);