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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Sat, 31 Dec 2011 10:05:38 -0700
Subject: Re: How to get function string name from i-th stack position?
To: Lie Ryan <lie.1296@gmail.com>
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On Sat, Dec 31, 2011 at 4:41 AM, Lie Ryan <lie.1296@gmail.com> wrote:
> On 12/31/2011 08:48 AM, Ian Kelly wrote:
>>
>>
>> But they are two distinct function objects, and there is no way
>> programmatically to determine that they are the same function except
>> by comparing the bytecode (which won't work generally because of the
>> halting problem).
>
>
> Actually, it is often possible to determine that two functions are the same
> function, you simply need a to compare whether the function object lives in
> the same memory address. It is also possible to determine if two functions
> are different, if the function object are in different memory address than
> the function is different function.
>
> What is difficult to do due to the Halting problem is comparing whether two
> different functions are "equivalent" (and therefore interchangeable).

Yes, that is what I said.  You can determine whether two function
objects are the same, but not whether they are *mathematically* the
same function.

> I think the OP wants to find the former, not the latter. The former is
> trivial, the latter impossible.

Based on his subsequent clarification, I agree, although from his
original post it sounded like he was just trying to identify summing
functions in general.   However, finding the built-in sum function on
the stack is not trivial at all, perhaps not even possible.