"Jonathan Turkanis" <technews@kangaroologic.com> wrote in message news:d22j79$ag5$1@sea.gmane.org...
David Abrahams wrote:
"Jonathan Turkanis" <technews@kangaroologic.com> writes:
Dear All,
Several months ago I became the official maintainer of Boost.Rational, and am just now getting around to considering proposed modifications to the library.
I would like to know:
1. Do people use Boost.Rational, and if so, what is it used for, and with what template parameters?
I'm not using it now, but I will probably want to throw it at my upcoming linear algebra code, using an unlimited precision integer type (if I can find one) as the template parameter.
Would it be kosher for me to grab a bigint class from the Yahoo files section -- say the one by Ronald Garcia and Andrew Lumsdaine -- make sure it is in good shape, and let it be the default template parameter to rational?
Surely int should be the default parameter (if any). Using bigint turns it from a relatively lightweight to a heavyweight type. In many uses of rational the values are unlikely to overflow. Some uses are in dividing a circle into degrees, minutes, or seconds, power of dimension in a runtime physical-quantity, Storing imperial lengths eg 1 1/8 " (inch). I would guess that these are the major uses of rational and all have values in quite a small range. And of course making bigint the default parameter introduces a dependency, which is at least untidy. As far as errors due to overflow, the problem is not actually in the domain of rational but of the value_type as has been stated before. rational shouldnt need to know anything about the behaviour of its value_types operations. BTW why doesnt boost::rational have a 'value_type' member rather than the obscure 'int_type'? Further If the mpl rational (or fraction) becomes part of boost: http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?MPL_TODO_List. it would be useful to allow interaction between the compile time and run time types: typedef boost::mpl::rational_c<int,1,360> ct; for (boost::rational<int> rt ; rt <= 1; rt += ct()){...} Other useful operation might be an integer_cast which throws if denominator != 1 regards Andy Little