txr: support @(if)/@(elif)/@(else) in @(output).

This turns out to be way easier than I thought.

* match.c (do_output_if): New static function.
(do_output): Handle if via do_output_if.

* parser.y (out_if_clause, out_elif_clauses_opt,
out_else_clause_opt): New nonterminal symbols and grammar
rules.
(out_clause): Now produces out_if_clause.
(not_a_clause): Remove ELIF and ELSE; these entries here cause
conflicts now. Here, continue to recognize the Lisp if, which
is distinguished by having at least two arguments.
out_if_clause matches only a one-argument if, and a
no-argumeent one that is diagnosed as erroneous.

* txr.1: Documented.

0 files changed, 0 insertions, 0 deletions