Programming question and strange == result
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10-08-2014, 10:14 PM
Post: #1
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Programming question and strange == result
Made a very simple test program:
Quote:EXPORT TEST(X,Y) Running; TEST(x^2+x-3,x-1) Results in: {(x^2+x-3)/(x-1),0} Running: quorem(x^2+x-3,x-1) Results in: [x+2 -1] Why does the program give me that result? Have spent ALOT of time trying to figure this out..any ideas? Another very strange thing I noticed: 2x-2==2(x-1) results in 0 2x-2==2x-2 results in 1 simplify(2x-2==2(x-1)) results in true simplify(2x-2==2x-2) results in 1 Any reasonable explanation for this? |
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10-09-2014, 06:12 PM
Post: #2
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RE: Programming question and strange == result
a==b checks if a and b have the same representation, it does not check if they are mathematically equivalent. For that the best is simplify(a-b)==0.
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10-09-2014, 06:59 PM
Post: #3
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RE: Programming question and strange == result
(10-09-2014 06:12 PM)parisse Wrote: a==b checks if a and b have the same representation, it does not check if they are mathematically equivalent. For that the best is simplify(a-b)==0. Thanks for your answer! What exactly does "the same representation" mean in this situation? Neither english or math ![]() Shouldn't at least this give the same result (true or 1 in both cases)? simplify(2x-2==2(x-1)) results in true simplify(2x-2==2x-2) results in 1 Any idea why quorem gives a different result inside/outside a program (and how to make it work within a program)? |
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10-10-2014, 05:47 AM
Post: #4
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RE: Programming question and strange == result
Same representation = same internal tree representation.
simplify(2x-2==2x-2) returns true in Xcas, I don't know why it does not on the Prime, maybe something fixed since last firmware release. For programs using CAS instructions, I would recommend using a CAS program not a HOME program. |
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11-01-2014, 07:08 AM
Post: #5
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RE: Programming question and strange == result
By the way, if you do a==b, the current version of Xcas does now compute the autosimplification function on a-b and checks if it's 0 or not. Therefore setting autosimplification to none, minimum or maximum might affect the == test on the Prime.
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