Fixing issue with list-like iteration over generic sequences,

namely that empty strings and vectors are not nil.
The nullify function is introduced. It is also exposed to
users, as is the existing make_like function.

* eval.c (mapcarv, mappendv, lazy_mapcar, lazy_mapcarv):
Use nullify to handle non-list inputs correctly.
(eval_init): Registering make_like and nullify as intrinsics.

* lib.c (copy_list, to_seq, list_collect_nconc, list_collect_append,
reverse, lazy_appendv_func, lazy_appendv, ldiff, memq, memql,
memqual, remq, remql, remqual, remove_if, keep_if, rem_lazy_rec,
remq_lazy, remql_lazy, remqual_lazy, remove_if_lazy, keep_if_lazy,
countqual, countql, countq, count_if, some_satisfy, all_satisfy,
none_satisfy, do_chain, chainv, do_and, andv, do_or, orv,
cat_vec, assoc, assql, mapcar, mapcon, mappend, sort, multi_sort,
find, find_if, posqual, posql, posq, pos, pos_if, set_diff,
search): Use nullify for correctness. Some functions fixed
so return sequence matches type of input sequence.
(nullify): New function.

* lib.h (nullify): Declared.

* txr.1: Documented nullify and ake-like.

1 files changed, 8 insertions, 4 deletions

diff --git a/eval.c b/eval.c
index a4f320ab..068e1a9e 100644
--- a/eval.c
+++ b/eval.c
@@ -2651,9 +2651,9 @@ static val macroexpand(val form, val menv)
 val mapcarv(val fun, val list_of_lists)
 {
   if (!cdr(list_of_lists)) {
-    return mapcar(fun, car(list_of_lists));
+    return mapcar(fun, nullify(car(list_of_lists)));
   } else {
-    val lofl = copy_list(list_of_lists);
+    val lofl = mapcar(func_n1(nullify), list_of_lists);
     val list_orig = car(list_of_lists);
     list_collect_decl (out, otail);
 
@@ -2679,7 +2679,7 @@ static val mappendv(val fun, val list_of_lists)
   if (!cdr(list_of_lists)) {
     return mappend(fun, car(list_of_lists));
   } else {
-    val lofl = copy_list(list_of_lists);
+    val lofl = mapcar(func_n1(nullify), list_of_lists);
     val list_orig = car(list_of_lists);
     list_collect_decl (out, otail);
 
@@ -2716,6 +2716,7 @@ static val lazy_mapcar_func(val env, val lcons)
 
 val lazy_mapcar(val fun, val list)
 {
+  list = nullify(list);
   if (!list)
     return nil;
   return make_lazy_cons(func_f1(cons(fun, list), lazy_mapcar_func));
@@ -2744,7 +2745,7 @@ static val lazy_mapcarv(val fun, val list_of_lists)
   } else if (some_satisfy(list_of_lists, null_f, identity_f)) {
     return nil;
   } else {
-    val lofl = copy_list(list_of_lists);
+    val lofl = mapcar(func_n1(nullify), list_of_lists);
     return make_lazy_cons(func_f1(cons(fun, lofl), lazy_mapcarv_func));
   }
 }
@@ -3530,6 +3531,9 @@ void eval_init(void)
   reg_fun(intern(lit("update"), user_package), func_n2(update));
   reg_fun(intern(lit("search"), user_package), func_n4o(search, 2));
 
+  reg_fun(intern(lit("make-like"), user_package), func_n2(make_like));
+  reg_fun(intern(lit("nullify"), user_package), func_n1(nullify));
+
   reg_fun(intern(lit("symbol-value"), user_package), func_n1(symbol_value));
   reg_fun(intern(lit("symbol-function"), user_package), func_n1(symbol_function));
   reg_fun(intern(lit("boundp"), user_package), func_n1(boundp));