call

/*
 *  call-seq:
 *     cont.call(args, ...) 
 *     cont[args, ...]
 *  
 *  Invokes the continuation. The program continues from the end of the
 *  <code>callcc</code> block. If no arguments are given, the original
 *  <code>callcc</code> returns <code>nil</code>. If one argument is
 *  given, <code>callcc</code> returns it. Otherwise, an array
 *  containing <i>args</i> is returned.
 *     
 *     callcc {|cont|  cont.call }           #=> nil
 *     callcc {|cont|  cont.call 1 }         #=> 1
 *     callcc {|cont|  cont.call 1, 2, 3 }   #=> [1, 2, 3]
 */

static VALUE
rb_cont_call(argc, argv, cont)
    int argc;
    VALUE *argv;
    VALUE cont;
{
    rb_thread_t th = rb_thread_check(cont);

    if (th->thread != curr_thread->thread) {
        rb_raise(rb_eRuntimeError, "continuation called across threads");
    }
    if (th->thgroup != cont_protect) {
        rb_raise(rb_eRuntimeError, "continuation called across trap");
    }
    switch (argc) {
      case 0:
        th->result = Qnil;
        break;
      case 1:
        th->result = argv[0];
        break;
      default:
        th->result = rb_ary_new4(argc, argv);
        break;
    }

    rb_thread_restore_context(th, RESTORE_NORMAL);
    return Qnil;
}