: static VALUE rb_yield_0(VALUE val, VALUE self, VALUE klass, int pcall) 
    ȥ֥å val Ϥƽܤ
    Τ self ȥ饹 self  klass ڤؤ롣
    Proc θƤӽФΤȤ pcall=󥼥 ˤʤФʤʤ

