[boost] Bug in boost::rational, no Boolean conversion; an operator template suggestion

From: Daryle Walker (darylew_at_[hidden])
Date: 2005-07-17 00:32:55

I'm writing a class template where the template parameter is a type that
should represent real numbers.  It started choking when using
boost::rational when I needed Boolean conversion, e.g.

template < typename T >
void  my_class<T>::my_func()
{
    if ( this->s_ )
        //...
}

Looking at boost::rational, I noticed that it does NOT have a Boolean
conversion operator (i.e. an unspecified numeric/pointer type).  Before
anyone says that's proper, realize that boost::rational DOES have "operator
not()" defined!  This is a surprise to the typical C++ programmer.  Either
both should be defined, or neither.  I think that boost::rational should add
a Boolean conversion.  (It's a quick fix, and it is critical, so it should
be done for this release.)

Incidentally, maybe we should define another helper template for
<boost/operators.hpp>.  If a type supports default construction and equality
via "operator ==()", then a Boolean conversion and "operator not()" will be
added.  (It's up to the user to make sure the type is numeric and the
default value is equivalent to zero.)

-- 
Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT hotmail DOT com