[ruby-core:24634] Re: [Bug #1844] Immediates Should Not Respond to :dup

Hi --

On Fri, 31 Jul 2009, Hongli Lai wrote:

> Issue #1844 has been updated by Hongli Lai.
>
>
> I disagree.
>
> - Exceptions are expensive.
> - Rescuing a specific exception requires a multi-line statement,
> while respond_to? allows one to write "bar.foo if
> bar.respond_to?(:foo)"

But you probably wouldn't do:

   x = y.dup if y.respond_to?(:dup)

because if it didn't, you'd end up with nil.

> - How do you know the exception was raised by the method itself and
> not by a method called by the method?

That's always a risk with exceptions, though, isn't it?

> You say respond_to? is not always reliable. I think it should be reliable.

I think that the exceptions and their messages can be useful in cases
like:

   (0.0..10.0).each {} # TypeError: can't iterate from float

as opposed to having float ranges not respond to #each, and having to
ask each range whether it responds to #each. I tend to see the
immediate.dup thing as similar to that.


David

-- 
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