New function: arithp.

* lib.h (arithp): Declared.
(plus_s): Existing symbol declared.

* arith.c (arithp): New function.

* struct.h (special_slot): New enum member plus_m.

* struct.c (special_sym): Register plus_s together as
the [plus_m] entry of the array.

* tests/016/arith.tl
* tests/016/ud-arith.tl: Tests for arithp.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.

1 files changed, 1 insertions, 0 deletions

diff --git a/struct.h b/struct.h
index 4b442fb7..213a4b91 100644
--- a/struct.h
+++ b/struct.h
@@ -39,6 +39,7 @@ enum special_slot {
   equal_m, nullify_m, from_list_m, lambda_m, lambda_set_m,
   length_m, car_m, cdr_m, rplaca_m, rplacd_m,
   iter_begin_m, iter_more_m, iter_item_m, iter_step_m, iter_reset_m,
+  plus_m,
   num_special_slots
 };