[GiNaC-list] Maps and sets of symbols?

Sheplyakov Alexei varg at theor.jinr.ru
Wed Sep 14 19:02:27 CEST 2005

On Thu, Sep 15, 2005 at 01:08:45AM +1000, John Pye wrote:
> I _really_ wanted to use
> std::map<symbol, symbol>
> What's a better idea then?

You can define ordering as

struct symbol_is_less 
 inline const bool operator()(const symbol& a, const symbol& b)
   return ex_is_less()(a, b);

and use

std::map<symbol, symbol, symbol_is_less>

Here is a simple example:

#include <iostream>
#include <iterator>
#include <map>
#include <ginac/ginac.h>
using namespace std;
using namespace GiNaC;

struct symbol_is_less 
 inline const bool operator()(const symbol& x, const symbol& y)
   return ex_is_less()(x, y);

typedef map<symbol, symbol, symbol_is_less> ssmap;

int main(int argc, char** argv)
	symbol x("x");
	symbol y("y");
	symbol z("z");
	symbol t("t");
	ssmap foo;
	foo[x] = z;
	foo[y] = t;
	for (ssmap::const_iterator i=foo.begin(); i!=foo.end(); ++i)
		cout << i->first << " ==> " << i->second << endl;

	return 0;

Is this good enough for your purpose?

Best regards,

All science is either physics or stamp collecting.
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