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April 2016

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Let's all embrace C++11 with the GiNaC 1.7.0 release
by Richard B. Kreckel 30 Apr '16

30 Apr '16

Hi, A new GiNaC release is out and available. Beginning with this release, GiNaC will not work with pre-C++11 compilers. The configure script will try to set the necessary compiler flags for you. Here's the news summary: * Make use of C++11 features: - Use new language features 'auto', 'nullptr', 'constexpr', range-based for loops, the contextual keyword 'override', static 'noexcept' operator, etc. - Add initializer list ctors for container<>, lst and nested initializer lists ctor for class matrix. - Add many rvalue reference overloads for ctors from std containers. (Note that whether they really speed up things depends on whether evaluation leaves the container unchanged or not.) - Rvalue reference overloads for ctors from std containers made it possible to remove the manual 'discardable' hack and std::auto_ptr<T> for good. - New dynallocate<T>(args...) helper functions obsolete manual allocation on the heap and setting the dynallocated status flag. - Got rid of C++98ish algorithm features (bind2nd, etc.) and replaced them with lambdas. * Make add::eval(), mul::eval() more careful so they return an evaluated, canonical expression without compromise. * Remove 'level' argument of all .eval() methods. This has become possible by ensuring that add::eval() and mul::eval() evaluate their own structure without compromise (this was not guaranteed before). If all ex are evaluated, any object which is an aggregate of such ex will only ever have to evaluate itself, obsoleting the need for recursing. * Remove 'level' arguments of all .evalf() and .normal() methods. They were modeled after the .eval() methods. * Make relational::rhs() and lhs() nonvirtual. * Add support for power::info(info_flags::real). * Add fderivative::derivatives() method. * Remove broken info_flags::algebraic. * Remove unmaintained support for Cint. * Remove unfinished andcode for hash table-based expairseq. * Remove deprecated ex::to_rational(lst) and ex::to_polynomial(lst). * ginac-excompiler installs in $LIBEXECDIR now, not in $BINDIR. * Many minor performance enhancements. Happy hacking -richy. PS: And to those on ginac-devel I apologize for my git tag abuse. -- Richard B. Kreckel <http://in.terlu.de/~kreckel/>

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Given a formal iterated derivative (GiNaC::fderivative), what actually is it?
by Ricardo Buring 14 Apr '16

14 Apr '16

Dear list, Using GiNaC one can define a symbolic/formal function f of two variables as follows: DECLARE_FUNCTION_2P(f) REGISTER_FUNCTION(f, dummy()) Formal derivatives can be computed by defining symbols x, y and calculating e.g. f(x,y).diff(x, 3).diff(y, 2) which is printed as D[0,0,0,1,1](f)(x,y) This is fantastic. Now, I would like to obtain the list [0, 0, 0, 1, 1] from the above expression. Checking the printing code GiNaC::fderivative::do_print, this is stored in a GiNaC::paramset. However, it's protected, and it doesn't seem to be accessible by any method. My attempt if (is_a<fderivative>(e)) { fderivative fder = ex_to<fderivative>(e); for (auto x : fder.parameter_set) cout << x << ", "; } therefore fails. Could an accessor or some such be implemented so this (basic) operation becomes possible? Best regards, Ricardo

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