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Re: Re: Re: More /.{I->-1} craziness

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  • Subject: [mg106425] Re: [mg106410] Re: [mg106370] Re: More /.{I->-1} craziness
  • From: Andrzej Kozlowski <akoz at>
  • Date: Tue, 12 Jan 2010 04:48:52 -0500 (EST)
  • References: <hic33e$595$> <> <> <>

> (I am not adding myself to their number).

Oops. I meant "I am now adding myself to their number".
On 12 Jan 2010, at 10:38, Andrzej Kozlowski wrote:

> The obvious argument against doing this is that there is no evidence 
at all that there is a demand would actually justify any effort in this 
> So far I have noticed just two voices in favor, the person who once 
wrote a Mathematica parser that has never been used by anyone (as far as 
I can tell), you and that seems to be all. Even the OP, after his post 
was answer, did not, as far as I can tell, support the idea of adding 
new facilities to Mathematica so that he would not need to learn about 
> On the other hand, I have seen quite many people writing that they see 
no need for anything of this kind (I am not adding myself to their 
> Obviously no well run company would ever embark on spending resources 
on something that may end up being never (or almost never) used.
> Andrzej Kozlowski
> On 12 Jan 2010, at 08:54, DrMajorBob wrote:
>> WRI has blithely broken user code in the past, so Bill's argument 
>> they shouldn't in THIS case rings hollow.
>> Bobby
>> On Mon, 11 Jan 2010 04:27:30 -0600, Richard Fateman 
>> <fateman at> wrote:
>>> Bill Rowe wrote:
>>>> On 1/8/10 at 4:15 AM, fateman at (Richard Fateman)
>>>> wrote:
>>>>> Bill Rowe said ...
>>>>> "Again, the choice is either understand this behavior and live 
>>>>> it or find different software. There isn't any other productive
>>>>> choice."
>>>>> Well, reporting something as a bug and hoping it will be fixed is
>>>>> another choice.
>>>> Reporting a behavior that works as designed as a bug and hoping
>>>> it will be "fixed" seems very unproductive to me.
>>> When one first reports a behavior that one believes is a bug, the
>>> natural hope is that it will be fixed.  To think otherwise is kind 
>>> pessimistic, perhaps depressing.  That's probably what motivated the
>>> original poster (not me.)
>>>> What is there
>>>> to "fix" if the program performs as designed?
>>> 1. There are many many changes, some incompatible, to programs that
>>> worked as designed in earlier versions of Mathematica. The design 
>>> apparently deemed unsatisfactory.
>>> 2. All programs perform as programmed. Absent any different design
>>> document, one could say that all programs operate as designed. After
>>> all, the performance of the program is completely designed by the
>>> program text, and it operates entirely according to the design.
>>> This is the Peewee Herman argument ("I meant to do that").
>>>>> And writing a version of the facility that does the
>>>>> right thing is another choice. (Any takers?)
>>>> It seems to me, the effort to do this for replacement rules and
>>>> ensure the result doesn't cause other problems is far greater
>>>> than the effort needed to understand the current design and use
>>>> it to get your desired result.
>>> You don't seem to understand "version of the facility".  No one 
would be
>>> forced to use such a version, and therefore one could always use the
>>> original version so as to be compatible with previous design 
>>> features, whatever).
>>>>> Either of these could be "productive".
>>>> This is highly debatable.
>>> Apparently :)
>>>>> Are Mathematica design decisions sacred or something?
>>>> Of course Mathematica design decisions are not sacred.
>>> Yet you say proposing changes would be "unproductive", quoting from 
>>> message above.
>>> But it is
>>>> highly desirable new versions of Mathematica run code written
>>>> for earlier versions.
>>> Of course, but that is not enforced by WRI. Why should you enforce 
>>> Your view would make it impossible to improve anything e.g. new
>>> integration results, which would be incompatible with previous 
>>> which might (for example) depend on certainly integration problems 
>>> being done by the Integrate program.
>>>> Altering design decisions almost certainly
>>>> means the new version will not run some code written for earlier
>>>> versions.
>>> Not necessarily. Sometimes the change will return all results that 
>>> previously computed, but will provide functionality over a new 
>>> too, as Integrate.
>>> One could have a situation in which all code written for the 
>>> version (that worked) will continue to work.
>>> A possible incompatibility would be one where previously the code 
>>> "error, cannot compute this"   and now it returns an answer.
>>> While it may have its place in the world of software, being 
>>> with all previous design decisions (and bugs!) is not a very 
>>> plan for a software system such as Mathematica.
>>>> So, altering design decisions is not something that
>>>> should be done lightly.
>>> That's why it should be discussed! Not dismissed out of hand.
>>>> I don't believe the existence of users who have not yet taken
>>>> the time to understand the current design is sufficient cause to
>>>> change the current design.
>>> Again, you insist that I am proposing changing the current design.
>>> 1. I think the current design is wrong. (or woefully 
>>> 2. I think a better facility can be designed and implemented.
>>>> Nor do I think you have made a strong
>>>> enough case to warrant a design change in this case.
>>> There are certainly arguments that this particular  rule/replacement
>>> facility "works" for writing certain low-level programs and that any
>>> change which would alter the results or slow down the computation 
>>> be avoided, at least for these pre-existing programs.  There are
>>> also clear arguments that a different facility should be presented
>>> to the (less sophisticated) user,  e.g. original poster.
>>>> But on this second point, I am not the one who needs to be
>>>> convinced. It is someone at WRI who could actually implement a
>>>> change and their management.
>>> I disagree.  All you have to do is use your experience, skill, and
>>> imagination, to think about what a GOOD substitution facility should 
>>> as to not confuse someone who merely knows mathematics, and does not
>>> have an interest in learning the subtleties of FullForm, Reduce,
>>> Eliminate, ....  Your ideas could then be implemented in a newly
>>> designed additional facility.
>>> RJF
>> --
>> DrMajorBob at

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