ruby-dev

前田です。

matz@netlab.co.jp (Yukihiro Matsumoto) writes:

> たぶんコンテキストの情報量は一緒です．普通はcall/ccのある言
> 語ではこれを使ってスレッドを実装するのは簡単なんですが，逆も
> 出来るかな．

以下の変更でとりあえず動きました。
# しかし問題が...。


call_cc {|c| $cont = c}
print "Hello, World!\n" 
$cont.call

のようなスクリプトを実行すると無限ループになります。

これはSchemeと同じ動作ではないのですが、それはさておき、irb上で、

irb(main):001:0> call_cc {|c| $cont = c}
#<Continuation:0x4015f7e0>
irb(main):002:0> print "Hello!\n"
Hello!
nil
irb(main):003:0> $cont.call
nil
irb(main):004:0> $cont
#<nil:0x4015f7e0>

などという不穏な動作をします。
# Continuationがnilになっている?

更に、

irb(main):001:0> cont = call_cc {|c| c}
#<Continuation:0x4015fc18>
irb(main):002:0> cont.call(cont)
/home/shugo/bin/irb.rb:417: [BUG] class path is not set properly
Aborted

とすると落ちてしまいます:-(

一体どこがまずいのでしょうか。

# irbでcall_ccした時に何が起こっているのか考えいたら頭がいたく
# なってきました。

-- 
前田 修吾 (mailto:shugo@aianet.ne.jp)

Attachments (1)

eval.c.diff (1.91 KB, text/x-diff)

--- eval.c.orig	Fri Jan  8 16:09:02 1999
+++ eval.c	Sat Jan  9 23:17:34 1999
@@ -6816,6 +6816,77 @@
     }
 }
 
+static VALUE rb_cContinuation;
+
+static VALUE
+rb_call_cc(self)
+    VALUE self;
+{
+    thread_t th = ALLOC(struct thread);
+
+    th->status = THREAD_RUNNABLE;
+
+    th->status = 0;
+    th->result = 0;
+    th->rb_errinfo = Qnil;
+
+    th->stk_ptr = 0;
+    th->stk_len = 0;
+    th->stk_max = 0;
+    th->wait_for = 0;
+    th->fd = 0;
+    th->delay = 0.0;
+    th->join = 0;
+
+    th->frame = 0;
+    th->scope = 0;
+    th->klass = 0;
+    th->dyna_vars = 0;
+    th->block = 0;
+    th->iter = 0;
+    th->tag = 0;
+    th->rb_errinfo = 0;
+    th->last_status = 0;
+    th->last_line = 0;
+    th->last_match = 0;
+    th->abort = 0;
+
+    th->thread = Data_Wrap_Struct(rb_cContinuation, thread_mark,
+				  thread_free, th);
+
+    FL_SET(ruby_scope, SCOPE_SHARED);
+    rb_thread_save_context(th);
+    if (setjmp(th->context)) {
+	return th->result;
+    }
+    else {
+	return rb_yield(th->thread);
+    }
+}
+
+static VALUE
+rb_continuation_call(argc, argv, cont)
+    int argc;
+    VALUE *argv;
+    VALUE cont;
+{
+    thread_t th = rb_thread_check(cont);
+
+    switch (argc) {
+    case 0:
+	th->result = Qnil;
+	break;
+    case 1:
+	th->result = *argv;
+	break;
+    default:
+	th->result = rb_ary_new4(argc, argv);
+	break;
+    }
+    rb_thread_restore_context(th, 0);
+    return th->result;
+}
+
 void
 Init_Thread()
 {
@@ -6855,6 +6926,13 @@
 
     /* allocate main thread */
     main_thread = rb_thread_alloc(rb_cThread);
+
+    rb_cContinuation = rb_define_class("Continuation", rb_cObject);
+    rb_undef_method(CLASS_OF(rb_cContinuation), "new");
+    rb_define_method(rb_cContinuation, "call", rb_continuation_call, -1);
+    rb_define_method(rb_mKernel, "call_with_current_continuation",
+		     rb_call_cc, 0);
+    rb_define_alias(rb_mKernel, "call_cc", "call_with_current_continuation");
 }
 #endif

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