TXR quasiliterals and output vars treated as Lisp.

* eval.c (format_field): Function moved here from match.c,
along with the introduction of a new behavior: if a meta-expr
occurs among the modifiers, its constituent expression
is evaluated in its place. This allows for @{a @[expr]}
which was previously not allowed in Lisp quasiliterals,
but worked in TXR quasiliterals due to the treatment
of @ by txeval.
(subst_vars): Static function turns external, so code in
match.c can call it instead of the subst_vars in that module.
For that purpose, it needs to take a filter argument and
process filters, like the match.c subst_vars.
(op_quasi_lit): Pass nil as filter argument to subst_vars.

* eval.h (format_field, subst_vars): Declared.

* match.c (format_field): Function removed, moved to
eval.c and slightly changed.
(subst_vars): Renamed to tx_subst_vars. By default, now just a
wrapper for subst_vars. In compatibility mode, invokes the
old logic.
(do_txeval, do_output_line): Call tx_subst_vars rather than
subst_vars.

* match.h (format_field): Declaration removed.

* parser.y (expr): Grammar production removed: no longer
referenced.
(o_var): Braced variable case now parsed as n_expr, and
expanded as expr by default, since this is Lisp now. In
compatibility mode, expanded using expand_meta.
Also SYMTOK case must be subject to expansion; an output
var can now be a symbol macro.
(expand_meta): Expand a quasi-literal as Lisp, except
in compatibility mode.

* txr.1: Bit of a documentation update. Existing doc isn't
totally clear.

1 files changed, 2 insertions, 0 deletions

diff --git a/eval.h b/eval.h
index 67254820..5fc4c516 100644
--- a/eval.h
+++ b/eval.h
@@ -59,6 +59,8 @@ val apply_intrinsic(val fun, val args);
 val eval_progn(val forms, val env, val ctx_form);
 val eval(val form, val env, val ctx_form);
 val eval_intrinsic(val form, val env);
+val format_field(val string_or_list, val modifier, val filter, val eval_fun);
+val subst_vars(val forms, val env, val filter);
 val load(val target);
 val expand(val form, val menv);
 val expand_forms(val forms, val menv);