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Re: "Do What I Mean" - a suggestion for improving

  • To: mathgroup at
  • Subject: [mg96991] Re: [mg96961] "Do What I Mean" - a suggestion for improving
  • From: DrMajorBob <btreat1 at>
  • Date: Sun, 1 Mar 2009 04:56:23 -0500 (EST)
  • References: <>
  • Reply-to: drmajorbob at

> Please reconsider my suggestion with this clarification in mind.

No thanks. Artificial intelligence is NECESSARY in the long run, but it's  
very far off.


On Sat, 28 Feb 2009 13:09:57 -0600, David Bakin <davidbak at> wrote:

> DrMajorBob,
> I think you're missing the point here - and actually, this is exactly the
> point that AES keeps banging on.  "It's up to a user to write what he  
> means"
> is small comfort to a user, especially one new to Mathematica, who  
> doesn't
> know how to express what he means.  Not only do we see a lot of comments  
> on
> this list of the form "Why doesn't this work?" we see a lot of the form
> "I've looked and looked and I can't figure out why this doesn't work".   
> And
> meanwhile, "xy" instead of "x y" is sitting there obvious as hell to all  
> of
> us who, in fact, do know what the user means.
> Perhaps you're hung up on the idea that I propose that DWIM be invoked
> automatically.  I didn't mean for everyone! Not you! And maybe not for
> anyone:  Just consider my idea that it is invoked by the user typing
> "Explain[]" after an evaluation of something that didn't go as he  
> expected.
> Then you have the proper conditions:  The user typed something, he didn't
> get the answer he wanted, he suspects it may be to his input being "not  
> what
> he meant", so he takes a positive action to find out why.  The Explain[]
> rule inspects In[] and Out[] and the environment and offers suggestions.
> When you say "DWIM is impossible even in theory" perhaps you didn't get  
> that
> "DWIM" is a tongue-in-cheek name, not to be taken literally.  It is just  
> a
> name for an meta-analysis feature that inspects the user's input and
> proposes similar input forms that may be closer to what the user has in
> mind, based on a database of common errors.
> Please reconsider my suggestion with this clarification in mind.
> -- David
> On Sat, Feb 28, 2009 at 10:12 AM, DrMajorBob <btreat1 at>  
> wrote:
>> Sorry, but most (maybe none) of that can be done. Point by point:
>> 1) x/xy is NOT a syntax error, and it may be exactly what I mean. It's  
>> up
>> to a user to write what he means.
>> 2) There are no "functions" in Mathematica; only rules. If you defined
>> f[x_Integer]:=x^2 and then tried to evaluate f[2.3] the first rule isn't
>> invoked because 2.3 doesn't fit the pattern, so Mathematica has no
>> opportunity to match it (since it DOESN'T match) and then TELL you it
>> doesn't match. This may be EXACTLY what I want and expect to happen, so  
>> it
>> would be a waste of time for Mathematica to flag this as an error every  
>> time
>> it occurs.
>> 3) NIntegrate, for instance, can only work if all variables and  
>> parameters
>> are numeric, and you already get an error message if they're not.  
>> Integrate,
>> on the other hand, can work with symbolic variables and numeric  
>> parameters.
>> There are a lot of case-by-case situations. I don't see how Mathematica
>> could guess whether you've tried what you meant to try. It only knows
>> (sometimes) how successful it was.
>> 4) When FindMinimum or NIntegrate or NDSolve has precision problems,
>> there's no way for Mathematica to know how to proceed. Sometimes you  
>> need a
>> new Method, other times a new WorkingPrecision, and often, you're  
>> simply NOT
>> going to integrate the thing you're trying to integrate, no matter WHAT  
>> you
>> do.
>> DWIM is impossible, even in theory.
>> Bobby
>> On Sat, 28 Feb 2009 05:42:20 -0600, David Bakin <davidbak at>
>> wrote:
>> A few days ago I posted that Mathematica should have a "DWIM" feature -  
>> "Do
>>> What I Mean".
>>> In InterLisp, in the 80's, the DWIM facility was hooked into error
>>> messages,
>>> and when invoked on a user error would poke around on the stack and in  
>>> the
>>> environment using some rules to describe common error situations and it
>>> would uncover user errors and offer to correct them.  Many of the  
>>> errors
>>> were simple spelling errors and it would correct a misspelled variable
>>> name
>>> if it found an unbound variable but a similarly spelled variable was  
>>> bound
>>> in the environment.
>>> Mathematica could benefit from this, and in fact, we at mathgroup could
>>> supply the rules (and framework) as a useful group project.
>>> If some guru would write the framework - trapping error messages  
>>> somehow,
>>> perhaps when they were written to the $Messages channel (by replacing  
>>> the
>>> default $Messages channel with something that would hook into the DWIM
>>> function), or perhaps with some other hook like redefining Message[] -
>>> then
>>> the rest of us could supply rules for the common errors.  Especially  
>>> the
>>> common errors we see puzzling Mathematica newbies on this list.
>>> I would suggest that the rules provide messages, hopefully with  
>>> hyperlinks
>>> to the documentation.
>>> A true DWIM might also offer to rewrite the current expression and try  
>>> it
>>> again, but I don't know if that can be done given the hooks into
>>> Mathematica
>>> that are currently available.
>>> Some situations that could be addressed are:
>>> 1.  User writes "xy" instead of "x y".  Rule could inspect the  
>>> expression
>>> under evaluation and find (unevaluated) symbols like "xy" of the form
>>> "<prefix><suffix>" where both "<prefix>" and "<suffix>" were either
>>> symbols
>>> used in the expression or symbols bound in the environment.  Rule would
>>> explain the problem and offer to rewrite expression and try again.
>>> 2.  Some expression using a user-defined function causes an error when
>>> evaluating, or doesn't evaluate.  Looking at the function, a rule finds
>>> function calls where the function arguments' patterns include  
>>> "_Integer"
>>> or
>>> similar but the arguments given to it are not integers.  Rule points to
>>> documentation describing argument types required by the called  
>>> function.
>>> 3.  Similar to 2 above, but it finds function calls that do numeric
>>> evaluation only or are optimized for numeric evaluation but the  
>>> arguments
>>> given to it are symbolic.
>>> 4.  Result returned is machine precision very close to zero (that is,
>>> with large negative exponent), but an error message complained of
>>> singularity, or other ill-conditioning.  Rule points to documentation
>>> explaining about machine precision, and/or singularity, and offers to
>>> retry
>>> the expression with more digits of precision, rewriting the expression  
>>> to
>>> achieve this.
>>> Actually, now that I think of it, the DWIM facility needs also to be
>>> invoked
>>> by the user because some of these situations don't cause error  
>>> messages,
>>> but
>>> only cause (wholly or partially) unevaluated expressions.  So maybe the
>>> user
>>> could be trained to type a word, like "Explain[]" after he didn't get  
>>> the
>>> result he wanted and the DWIM facility would look at the In[] and Out[]
>>> arrays to find out what he's been doing recently.
>>> I would be glad to contribute rules to the framework ... but I'm not  
>>> yet
>>> up
>>> to writing the framework.  Hopefully one of the gurus here will find  
>>> this
>>> interesting (and possible) and provide a framework.  Then the rest of  
>>> us
>>> could contribute rules that would improve the Mathematica experience  
>>> for
>>> all
>>> newcomers.  (AES, I'm looking at you! :-) )
>>> -- David
>> --
>> DrMajorBob at

DrMajorBob at

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