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Robert Israel

6522 Reputation

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18 years, 182 days
University of British Columbia
Associate Professor Emeritus
North York, Ontario, Canada
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MaplePrimes Activity


These are replies submitted by Robert Israel

prep2trans...

Robert Israel 6522
August 06 2007
prep2trans will make a sum into a loop, but it doesn't do anything with a product. It also seems unable to handle anything containing I. 
> with(codegen):
  prep2trans(proc(a,b) Re(a+I*b) end proc);
Error, (in intrep/statement) unable to translate I 
> prep2trans(proc(a,n) local i; product(a,i=1..n) end proc);
proc (a, n) local i; product(a,i = 1 .. n) end proc

puzzling substitution...

Robert Israel 6522
August 06 2007
In Maple 11 that gives me proc () local i; for i to 3 while false do false end do end proc Perhaps you mean 
subs(true = false, 
  proc()  to 3 do true; end do end proc);

Process names...

Robert Israel 6522
August 06 2007
0 0
Also mserver.exe, cwmaple.exe, or (in Maple 9.5) java.exe. Any other names? I'm not sure it's Microsoft's fault: under some circumstances, Maple might not shut itself down properly.

Process names...

Robert Israel 6522
August 06 2007
Also mserver.exe, cwmaple.exe, or (in Maple 9.5) java.exe. Any other names? I'm not sure it's Microsoft's fault: under some circumstances, Maple might not shut itself down properly.

Good question...

Robert Israel 6522
August 05 2007
0 0
I think that would be a very good idea.

Good question...

Robert Israel 6522
August 05 2007
I think that would be a very good idea.

Massive parse...

Robert Israel 6522
August 02 2007
Actually that should be "a single statement", not "a single line". You could also use any of these: 
> parse(cat("if true then ",str," fi;", statement);
> parse(cat("try ",str," end;", statement);
> parse(cat("use zero=0 in ",str," end;", statement);

Min vs first...

Robert Israel 6522
August 02 2007
0 0
My reading of the original question was that it was the first integer, rather than the least integer, that was wanted. There actually is a Maple procedure that searches a set or list for the first element of a given type. If L is your input, you could try this: 
> if membertype(integer, L, 'p') then L[p] fi;

Min vs first...

Robert Israel 6522
August 02 2007
My reading of the original question was that it was the first integer, rather than the least integer, that was wanted. There actually is a Maple procedure that searches a set or list for the first element of a given type. If L is your input, you could try this: 
> if membertype(integer, L, 'p') then L[p] fi;

Not very efficient...

Robert Israel 6522
August 01 2007
Your algorithm is indeed not very efficient, but that's hardly surprising: the problem of deciding whether a Boolean expression in sum-of-products form is equivalent to "true" is equivalent to the satisfiability problem SAT for the negation of the expression, and this is NP-complete. So (pending the solution of the P vs NP question) you're not going to find a polynomial-time algorithm for this.

minimal vs minimum...

Robert Israel 6522
July 31 2007
Your code also might not return a minimum sum. Consider this one: 
 > minbool("EACDB'+ECA'DB'+CDB'E'A+CDB'A'E'+EBA'CD+EBA'CD'\
+EBA'C'D+EBA'C'D'+C'BAED+C'BAED'+C'BAE'D+C'BAE'D'+ADE'BC\
+ADE'B'C'+D'ACEB+D'ACEB'+D'ACE'B+D'ACE'B'");

*** Max loops in concensusList reached, terminating ***
Minimal sum: ADE' + A'EDB + EC'B + CB'D + ECD'B + ACB' + AD'B
A minimum sum, I think, is CDB'+EBA'+ABC'+ADE'+ACD'.

Oops...

Robert Israel 6522
July 29 2007
Oh, sorry, I guess I didn't notice that this was wrong... Yes, it looks like a serious bug. Maple is treating ln(ln(x)) and ln(x) as variables independent of x.

No, we haven't...

Robert Israel 6522
July 28 2007
This is not usual. It depends, I guess, on exactly what Maple is doing in those 2 or 3 hours. The details are important. If it's doing some very complicated computations that fill up all the available memory with their results, then this could happen. Perhaps if you tell us what you're trying to do and how you're trying to do it, somebody can suggest a way of avoiding this problem.

It worked for me...

Robert Israel 6522
July 28 2007
That's strange. It worked for me in Maple 11.01. I tried several times, using different orderings for the variables, and it always worked. Can you upload a worksheet that shows it not working?

BooleanSimplify...

Robert Israel 6522
July 27 2007
Isn't this functionality provided (using other notation) by BooleanSimplify in the Logic package?
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