Module#included_modules によってモジュール(含クラス)が include
しているモジュールの一覧を得ることができますが、 Module A が
Module B を include しているかどうかを調べるのに

	A.included_modules.include?(B)

というのは回りくどい感じがするので、 Module#include? を導入して

	A.include?(B)

で判定できるようにするというのはどうでしょうか?

-- 
                     /
                    /__  __            Akinori.org / MUSHA.org
                   / )  )  ) )  /     FreeBSD.org / Ruby-lang.org
Akinori MUSHA aka / (_ /  ( (__(  @ iDaemons.org / and.or.jp

"Freeze this moment a little bit longer, make each impression
  a little bit stronger..  Experience slips away -- Time stand still"

Index: class.c
===================================================================
RCS file: /src/ruby/class.c,v
retrieving revision 1.20
diff -u -r1.20 class.c
--- class.c	2001/07/18 05:55:20	1.20
+++ class.c	2001/07/19 18:00:46
@@ -329,6 +329,22 @@
 }
 
 VALUE
+rb_mod_include_p(mod, mod2)
+    VALUE mod, mod2;
+{
+    VALUE p;
+
+    Check_Type(mod2, T_MODULE);
+
+    for (p = RCLASS(mod)->super; p; p = RCLASS(p)->super) {
+	if (BUILTIN_TYPE(p) == T_ICLASS && RBASIC(p)->klass == mod2) {
+	    return Qtrue;
+	}
+    }
+    return Qfalse;
+}
+
+VALUE
 rb_mod_included_modules(mod)
     VALUE mod;
 {
Index: object.c
===================================================================
RCS file: /src/ruby/object.c,v
retrieving revision 1.55
diff -u -r1.55 object.c
--- object.c	2001/07/18 05:55:20	1.55
+++ object.c	2001/07/19 18:00:46
@@ -1231,6 +1231,7 @@
     rb_define_method(rb_cModule, "clone", rb_mod_clone, 0);
     rb_define_method(rb_cModule, "dup", rb_mod_dup, 0);
     rb_define_method(rb_cModule, "to_s", rb_mod_to_s, 0);
+    rb_define_method(rb_cModule, "include?", rb_mod_include_p, 1);
     rb_define_method(rb_cModule, "included_modules", rb_mod_included_modules, 0);
     rb_define_method(rb_cModule, "name", rb_mod_name, 0);
     rb_define_method(rb_cModule, "ancestors", rb_mod_ancestors, 0);
Index: intern.h
===================================================================
RCS file: /src/ruby/intern.h,v
retrieving revision 1.55
diff -u -r1.55 intern.h
--- intern.h	2001/07/18 05:55:20	1.55
+++ intern.h	2001/07/19 18:00:47
@@ -89,6 +89,7 @@
 VALUE rb_define_class_id _((ID, VALUE));
 VALUE rb_module_new _((void));
 VALUE rb_define_module_id _((ID));
+VALUE rb_mod_include_p _((VALUE, VALUE));
 VALUE rb_mod_included_modules _((VALUE));
 VALUE rb_mod_ancestors _((VALUE));
 VALUE rb_class_instance_methods _((int, VALUE*, VALUE));