[ruby-dev:9019] Re: [PATCH] Array#flatten! for recursive array

なかだです。

At Tue, 25 Jan 2000 12:48:55 +0900,
Shin-ichiro Hara <[e-mail]> wrote:
> ||a = []; a << a; a.flatten!
> ||
> ||が返って来なかったりするのも一緒に変更しちゃってますが、あるいは
> ||こういう再帰的な構造に対して flatten! を使おうというがそもそも間
> ||違ってるんでしょうか。いっそ raise すべき?
> |
> |こっちは私にはなかなか判断できません。flattenの大家(というか
> |生みの親)である原先生のご意見を伺いたいです。
> 
> 私は無限ループになっても文句は言えないけど、
> できれば raise してあげるのが親切だと思います。

  んでは。しかし、よく悩むんですが、こういうときって何を raise す
るのがいいんでしょうか。とりあえず RuntimeError にしてみましたが…。


Index: ChangeLog
===================================================================
RCS file: /home/cvs/ruby/ChangeLog,v
retrieving revision 1.36
diff -u -2 -p -r1.36 ChangeLog
--- ChangeLog	2000/01/18 06:09:02	1.36
+++ ChangeLog	2000/01/25 21:37:39
@@ -1,2 +1,10 @@
+Wed Jan 26 06:18:35 2000  Nakada.Nobuyoshi  <[e-mail]>
+
+	* array.c (rb_protect_inspect, rb_inspecting_p): avoiding infinite
+	  recursive call for self recursive arrays.
+
+	* array.c (rb_ary_flatten_bang): now raises for self recursive
+	  arrays.
+
 Tue Jan 18 12:24:28 2000  Yukihiro Matsumoto  <[e-mail]>
 
Index: array.c
===================================================================
RCS file: /home/cvs/ruby/array.c,v
retrieving revision 1.11
diff -u -2 -p -r1.11 array.c
--- array.c	2000/01/18 06:09:02	1.11
+++ array.c	2000/01/25 21:37:44
@@ -791,6 +791,6 @@ rb_protect_inspect(func, obj, arg)
 {
     struct inspect_arg iarg;
-
     VALUE inspect_tbl;
+    VALUE id;
 
     if (!inspect_key) {
@@ -802,8 +802,9 @@ rb_protect_inspect(func, obj, arg)
 	rb_thread_local_aset(rb_thread_current(), inspect_key, inspect_tbl);
     }
-    if (rb_ary_includes(inspect_tbl, obj)) {
+    id = rb_obj_id(obj);
+    if (rb_ary_includes(inspect_tbl, id)) {
 	return (*func)(obj, arg);
     }
-    rb_ary_push(inspect_tbl, obj);
+    rb_ary_push(inspect_tbl, id);
     iarg.func = func;
     iarg.arg1 = obj;
@@ -822,5 +823,5 @@ rb_inspecting_p(obj)
     inspect_tbl = rb_thread_local_aref(rb_thread_current(), inspect_key);
     if (NIL_P(inspect_tbl)) return Qfalse;
-    return rb_ary_includes(inspect_tbl, obj);
+    return rb_ary_includes(inspect_tbl, rb_obj_id(obj));
 }
 
@@ -1501,4 +1502,5 @@ rb_ary_flatten_bang(ary)
     long i;
     int mod = 0;
+    VALUE flattening = Qnil;
 
     rb_ary_modify(ary);
@@ -1506,4 +1508,14 @@ rb_ary_flatten_bang(ary)
 	VALUE ary2 = RARRAY(ary)->ptr[i];
 	if (TYPE(ary2) == T_ARRAY) {
+	    VALUE id = rb_obj_id(ary2);
+	    if (ary == ary2) {
+	      recursive:
+		rb_raise(rb_eRuntimeError, "self recursive array");
+	    } else if (NIL_P(flattening)) {
+		flattening = rb_ary_new();
+	    } else if (rb_ary_includes(flattening, id)) {
+		goto recursive;
+	    }
+	    rb_ary_push(flattening, id);
 	    rb_ary_replace(ary, i--, 1, ary2);
 	    mod = 1;

-- 
そうだ 強気に ちょっと インチキに☆彡
    中田 "Bugるくらいがちょうどいいかも;-)" 伸悦