Hello! Some people claim that extending GiNaC is "unnecessary complex" (see e.g. http://www.ginac.de/pipermail/ginac-list/2006-July/000882.html). So I think it is good idea to provide self-contained, minimalistic example of a GiNaC class. The actual code is copy/pasted from the tutorial. --- doc/examples/Makefile.am | 3 +- doc/examples/mystring.cpp | 104 +++++++++++++++++++++++++++++++++++++++++++++ doc/tutorial/ginac.texi | 3 +- 3 files changed, 108 insertions(+), 2 deletions(-) diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am index 5ee2c5d..e63da35 100644 --- a/doc/examples/Makefile.am +++ b/doc/examples/Makefile.am @@ -1,6 +1,7 @@ ## Process this file with automake to produce Makefile.in -EXFILES = archive1.cpp compile1.cpp compile2.cpp compile3.cpp lanczos.cpp +EXFILES = archive1.cpp compile1.cpp compile2.cpp compile3.cpp lanczos.cpp \ + mystring.cpp TEXI = ginac-examples.texi diff --git a/doc/examples/mystring.cpp b/doc/examples/mystring.cpp new file mode 100644 index 0000000..cf0d8a2 --- /dev/null +++ b/doc/examples/mystring.cpp @@ -0,0 +1,104 @@ +/** + * @file mystring.cpp Example of extending GiNaC: writing new classes + */ +#include <iostream> +#include <string> +#include <stdexcept> +using namespace std; + +#include <ginac/ginac.h> +using namespace GiNaC; + +class mystring : public basic +{ + GINAC_DECLARE_REGISTERED_CLASS(mystring, basic) + +public: + mystring(const string &s); + mystring(const char *s); + ex eval(int level) const; + +private: + string str; + +protected: + void do_print(const print_context &c, unsigned level = 0) const; + +}; + +GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(mystring, basic, + print_func<print_context>(&mystring::do_print)) + +// ctors +mystring::mystring() : inherited(&mystring::tinfo_static) { } +mystring::mystring(const string &s) : inherited(&mystring::tinfo_static), str(s) { } +mystring::mystring(const char *s) : inherited(&mystring::tinfo_static), str(s) { } + +// comparison +int mystring::compare_same_type(const basic &other) const +{ + const mystring &o = static_cast<const mystring &>(other); + int cmpval = str.compare(o.str); + if (cmpval == 0) + return 0; + else if (cmpval < 0) + return -1; + else + return 1; +} + +// archiving/unarchiving +mystring::mystring(const archive_node &n, lst &sym_lst) : inherited(n, sym_lst) +{ + n.find_string("string", str); +} + +void mystring::archive(archive_node &n) const +{ + inherited::archive(n); + n.add_string("string", str); +} + +ex mystring::unarchive(const archive_node &n, lst &sym_lst) +{ + return (new mystring(n, sym_lst))->setflag(status_flags::dynallocated); +} + +// printing +void mystring::do_print(const print_context &c, unsigned level) const +{ + // print_context::s is a reference to an ostream + c.s << '\"' << str << '\"'; +} + +/** + * evaluation: all strings automatically converted to lowercase with + * non-alphabetic characters stripped, and empty strings removed + */ +ex mystring::eval(int level) const +{ + string new_str; + for (size_t i=0; i<str.length(); i++) { + char c = str[i]; + if (c >= 'A' && c <= 'Z') + new_str += tolower(c); + else if (c >= 'a' && c <= 'z') + new_str += c; + } + + if (new_str.length() == 0) + return 0; + else + return mystring(new_str).hold(); +} + +int main(int argc, char** argv) +{ + ex e = mystring("Hello, world!"); + cout << is_a<mystring>(e) << endl; + cout << ex_to<basic>(e).class_name() << endl; + cout << e << endl; + ex another = pow(mystring("One string"), 2*sin(Pi-mystring("Another string"))); + cout << another << endl; + return 0; +} diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi index a6befad..b2038db 100644 --- a/doc/tutorial/ginac.texi +++ b/doc/tutorial/ginac.texi @@ -7823,7 +7823,8 @@ Now we will start implementing a new class @code{mystring} that allows placing character strings in algebraic expressions (this is not very useful, but it's just an example). This class will be a direct subclass of @code{basic}. You can use this sample implementation as a starting point -for your own classes. +for your own classes @footnote{The self-contained source for this example is +included in GiNaC, see the @file{doc/examples/mystring.cpp} file.}. The code snippets given here assume that you have included some header files as follows: -- 1.4.4.4 Best regards, Alexei -- All science is either physics or stamp collecting.