Hi Neven, > Suppose I have code like this: > > l := [44, 178, 412, 746, 1168, 1669, 2260, 2941, 3712, 4573, 5524, 6565] > guess(l).1 > > Replacing the "guess" with a "guessRat" is essentially the same thing AFAIU. > > The above code returns a value of type Expression(Integer) that > represents (visually, at least) a recurrence relation. The recurrence > relation obviously defines a rational function, which means the > operation was technically a success. > > The problem is that if I try to convert the Expression to an actual > rational function in a naive manner, as illustrated in the following, > the conversion fails: > > guess(l).1::Fraction(Polynomial(Integer))
Welcome. ;-) To tell the truth, when I tried to use the guessing package for the first time, I ran into the same problem. The user interface is not very intuitive. One has to be familiar with the Expression domain to turn the result in something useful for further computation. But more importantly, one must look up the code of guess, guessRat and guessHPaux https://github.com/fricas/fricas/blob/master/src/algebra/mantepse.spad#L3381 in order to learn what the actual structure of the result is. Then you find that there is RecurrenceOperator. So do it this way: l := [44, 178, 412, 746, 1168, 1669, 2260, 2941, 3712, 4573, 5524, 6565] Z ==> Integer E ==> Expression Z K ==> Kernel E ROZE ==> RecurrenceOperator(Z, E) e1 := guess(l).1 e2 := getEq(e1)$ROZE k2 := mainKernel(e2)::K How to continue to actually get the other parts out of the result, is probably a matter of taking things apart with "Expression(Integer)" means, probably, isPlus and isTimes, etc. I definitely agree that this must be improved. Definitely there should be better documentation of how to take apart the result. Finding that RecurrenceOperator is the key, is unnecessarily hard and involves looking into the .spad files. Can you file a bug report at github? Thanks Ralf -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/fricas-devel/5c768a49-8895-af72-83d3-c085611f1820%40hemmecke.org.
