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, 4 insertions, 0 deletions

diff --git a/match.h b/match.h
index 2d710593..59f61f0c 100644
--- a/match.h
+++ b/match.h
@@ -30,6 +30,10 @@ extern val text_s, choose_s, gather_s, do_s, mdo_s, require_s, in_package_s;
 extern val close_s, load_s, include_s, mod_s, modlast_s, line_s;
 extern val else_s, elif_s;
 extern val counter_k, vars_k, lists_k, env_k, var_k, into_k, named_k, noclose_k;
+extern val append_k, continue_k, finish_k;
+
+extern val v_output_keys;
+
 val match_expand_keyword_args(val elem);
 val match_expand_elem(val elem);
 val match_filter(val name, val arg, val other_args);