* eval.c (apply): Pass missing optional arguments as colon_k.

to functions for which this is requested.
(reg_fun_mark): New static function.
(eval_init): Register reduce_left and reduce_right as requiring
marking for missing optionals.

* lib.c (func_set_mark_missing): New function.
(generic_funcall): Pass missing optional arguments as colon_k
to functions for which this is requested.
(reduce_left, reduce_right): Handle missing values of init and key.
(func_f0, func_f1, func_f2, func_f3, func_f4, func_n0, func_n1,
func_n2, func_n3, func_n4, func_n5, func_n6, func_n7, func_f0v,
func_f1v, func_f2v, func_f3v, func_f4v, func_n0v, func_n1v,
func_n2v, func_n3v, func_n4v, func_n5v, func_n6v, func_n7v):
Initialize new mark_missing_args member of struct func.

* lib.h (struct func): New bitfield member, mark_missing_args.
(func_set_mark_missing): Declared.
(missingp, null_or_missing_p): New inline functions.

* txr.1: Updated descriptions of reduce-left and reduce-right.

1 files changed, 6 insertions, 1 deletions

diff --git a/lib.h b/lib.h
index dfc68db0..03a67406 100644
--- a/lib.h
+++ b/lib.h
@@ -106,7 +106,7 @@ struct func {
   unsigned fixparam : 7; /* total non-variadic parameters */
   unsigned optargs : 7;  /* fixparam - optargs = required args */
   unsigned variadic : 1;
-  unsigned : 1;
+  unsigned mark_missing_args: 1; /* missing opt. args given as special value */
   unsigned functype : 16;
   val env;
   union {
@@ -601,6 +601,7 @@ val func_interp(val env, val form);
 val func_get_form(val fun);
 val func_get_env(val fun);
 val func_set_env(val fun, val env);
+val func_set_mark_missing(val fun);
 val functionp(val);
 val interp_fun_p(val);
 val funcall(val fun);
@@ -717,6 +718,10 @@ INLINE val nullp(val v) { return v ? nil : t; }
 
 #define nao ((obj_t *) (1 << TAG_SHIFT)) /* "not an object" sentinel value. */
 
+INLINE val missingp(val v) { return v == colon_k ? t : nil; }
+
+INLINE val null_or_missing_p(val v) { return (!v || v == colon_k) ? t : nil; }
+
 #define if2(a, b) ((a) ? (b) : nil)
 
 #define if3(a, b, c) ((a) ? (b) : (c))