[seqfan] Re: Maple strongly discouraged

[Neil Sloane]

Robert, I was quoting Russell Walsmith,
from an email to seq fans this morning,
as follows:

(quote)

[seqfan] Re: Re Nice variant on A030067
Russell Walsmith ixitol at gmail.com via list.seqfan.eu
9:59 PM (17 hours ago)

to Sequence
Just found this A109671 entry... pretty cool. But the Maple code, cut and
pasted into Maple 17, gives me the sequence
1, 1, 2, 1, 1, 2, 1, 1, 4, 3, 3, 2, 7, 5, 6, 1, 15, 6, 11, 3, 20, 9, 17, 2,
33, 11, 26, 5, 43, 16, 37, 1...

Any suggestions?

Russell
(end quote)

Here is what the code was:

> f:=proc(n) option remember; local t1;
> if n = 1 then RETURN(1);
> elif n mod 2 = 0 then RETURN(f(n/2));
> else t1:= f(n-2)-f((n-1)/2);
> if t1 > 0 then RETURN(t1) else RETURN(f(n-2)+f((n-1)/2)); fi; fi; end;

I replaced it by one M Hasler sent,
which avoided using RETURN

Neil



On Sun, Jan 12, 2014 at 2:59 PM, <israel at math.ubc.ca> wrote:

> How and when does it produce incorrect answers in Maple 17? In my copy of
> Maple 17 (actually Maple 17.02), as far as I can tell it produces the same
> results as the current updated version.
>
> Cheers,
> Robert Israel
>
>
>
>
>
> On Jan 12 2014, Neil Sloane wrote:
>
>  Dear Seq Fans, Maximilian Hasler has pointed out that
>> my Maple program in A109671 (which worked correctly in Maple 16)  no
>> longer gives correct results in Maple 17 because it used the RETURN()
>> command.
>>
>> The Maple web site says
>>
>> "use of the RETURN procedure is strongly discouraged"
>>
>> and I can see why - it produces incorrect answers (without any warning).
>> Of
>> course I don't see WHY they did this.
>>
>> Now there over 1900 Maple lines in the OEIS that use the RETURN statement.
>> Maybe these lines need a comment saying:
>>
>> # Warning: May give incorrect answers because Maple has changed the
>> meaning
>> of RETURN. Suggest switching to Mathematica instead.
>>
>> (Not sure about the second part)
>>
>> I could (and probably will have to) do this with a global edit.
>> Is there any other solution?  It is unethical for us to include programs
>> that give wrong answers.
>>
>> Here's the Maple program that works correctly in Maple 16 but gives wrong
>> answers  in Maple 17:
>>
>>  f:=proc(n) option remember; local t1;
>>>
>>
>>  if n = 1 then RETURN(1);
>>>
>>
>>  elif n mod 2 = 0 then RETURN(f(n/2));
>>>
>>
>>  else t1:= f(n-2)-f((n-1)/2);
>>>
>>
>>  if t1 > 0 then RETURN(t1) else RETURN(f(n-2)+f((n-1)/2)); fi; fi; end;
>>>
>>
>> Neil
>>
>>
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>
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>



-- 
Dear Friends, I have now retired from AT&T. New coordinates:

Neil J. A. Sloane, President, OEIS Foundation
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com