- GiNaC-list - ginac.de

Exceptions.
by Tatiana Zolo 03 Oct '02

03 Oct '02

Hi. I have problems in understanding GiNaC policy regarding the choice of exceptions thrown. The operator `operator/' defined on objects of the class `numeric' throws a `runtime_error' in the case of a division by zero. In contrast, the `operator/' defined on objects of the class `ex' throws a `logic_error' in the case of a division by zero. Why is there such a difference? According to the standard, the exception `logic_error' should be used when errors could have been detected before program execution: I thus believe that a `runtime_error' should be thrown even in the case of an `ex' object. The same argument hold for the exception thrown by `power': logic_error: power::eval(): division by zero. Thanks Tatiana Zolo

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Behavior of numeric::to_int() and numeric::to_long()
by Roberto Bagnara 01 Oct '02

01 Oct '02

These methods, and the corresponding functions taking the argument as a const numeric& parameter, when something goes wrong print a line of the form Not a 32-bit integer: -9223372028264841216 on cerr and exit the program. Wouldn't throwing a suitable standard exception (like std::domain_error) be a better option? All the best Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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Last in this series: behavior of irem()
by Roberto Bagnara 01 Oct '02

01 Oct '02

The function numeric irem(const numeric &a, const numeric &b) prints "Division by zero." and exits when b is zero. As in all the other cases reported, this makes it more difficult to write robust software. Of course, we can check b before calling irem() (and we are doing it) but this impedes performance for no reason, since the test on b must be re-done anyway in order to decide whether to print the error message and exit. All the best Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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Behavior of numeric::is_prime()
by Roberto Bagnara 01 Oct '02

01 Oct '02

In an attempt to invent documentation for the GiNaC facilities we use, we came across the following inconsistency in the behavior of the method bool numeric::is_prime(void) const and the function bool is_prime(const numeric &x), whereby exit(1) is called (via cl_abort()) if the number to be tested is a non-positive integer. I believe is_prime() should return false in this case, as it does for, e.g., -2/7, 2/7, 3*I, and 2.8943657489. All the best Roberto P.S. I am not including a patch since this issues may be dealt with either in CLN (which I believe is the better option) or in GiNaC. -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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Missing namespace qualification
by Roberto Bagnara 29 Sep '02

29 Sep '02

The patch below should be applied to GiNaC 1.0.11. All the best Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it diff -c -d -r1.1.1.1 function.h *** ginac/function.h 29 Sep 2002 13:26:57 -0000 1.1.1.1 --- ginac/function.h 29 Sep 2002 14:02:48 -0000 *************** *** 416,422 **** } #define is_ex_the_function(OBJ, FUNCNAME) \ ! (GiNaC::is_exactly_a<GiNaC::function>(OBJ) && GiNaC::ex_to<GiNaC::function>(OBJ).get_serial() == function_index_##FUNCNAME) } // namespace GiNaC --- 416,422 ---- } #define is_ex_the_function(OBJ, FUNCNAME) \ ! (GiNaC::is_exactly_a<GiNaC::function>(OBJ) && GiNaC::ex_to<GiNaC::function>(OBJ).get_serial() == GiNaC::function_index_##FUNCNAME) } // namespace GiNaC

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Accuracy of print_csrc_double
by Pearu Peterson 23 Sep '02

23 Sep '02

Hi, Is it possible to increase the accuracy of print_csrc_double output? print_csrc_double in GiNaC-1.0.8 shows only 6 decimal digits but I would like to have at least 16 digits displayed. Is it possible? Thanks, Pearu

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Documentation of prem()
by Tatiana Zolo 23 Sep '02

23 Sep '02

Dear all, the documentation about the function prem() (section 5.5.3 of GiNaC 1.0.11) says that the pseudo-remainder of 'a' and 'b' satisfies c*a = b*q + prem(a, b, x), where c = b.lcoeff(x)^(a.degree(x) - b.degree(x) + 1). I think there is maybe a mistake (probably a printing mistake), the formula should be c*a = c*b*q + prem(a, b, x), where c = b.lcoeff(x)^(a.degree(x) - b.degree(x) + 1). Regards, Tatiana Zolo

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Function `lsolve()'
by Tatiana Zolo 18 Sep '02

18 Sep '02

Dear all, we need to use the function `lsolve()' that appears on page 5 of the tutorial for GiNaC 1.0.10, but not in the Concept Index. We couldn't find it elsewhere, not even in the specifications for the class matrix. We would like to know its specifications, if possible. In particular, we have linear systems whose associated matrix may have some linear dependencies. Thank you very much in advance Alessandro Zaccagnini and Tatiana Zolo

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Neue Version
by Jens Vollinga 18 Sep '02

18 Sep '02

1.0.11 da ist.

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gcd() and lcm()
by Alessandro Zaccagnini 16 Sep '02

16 Sep '02

Dear all, we just tried to use the functions gcd() and lcm() and we found something strange. >gcd(2*x+1, x+1/2); 1 >gcd(2*x+1, 4*x+2); 1+2*x The documentation (section 5.5.5 of GiNaC 1.0.10) says that gcd() accepts two expressions, without specifying their type. In the last sentence, it talks about polynomials, again, without specifying whether they are integer polynomials or they are allowed to have rational coefficients. Since we need the functions gcd() and lcm() very often, we would like to know as precisely as possible what is the intended behaviour. Thank you very much Alessandro Zaccagnini and Tatiana Zolo

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