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From: Moore, Paul (paul.moore_at_[hidden])
Date: 2000-10-18 09:47:30

From: David Abrahams [mailto:abrahams_at_[hidden]]
> I was just trying to use boost::rational<>
> to test out new support for numeric types in
> py_cpp, and I'm finding the documentation
> missing quite a lot of important info. For
> example, what are the constructors? How do you
> access the numerator and denominator? I think
> what's missing here is basically a table which
> describes everything in the interface.

The information is there, but I'd agree it's a bit non-obvious.

Rationals can be constructed from a pair (numerator, denominator) of
integers, or a single integer. There is also a default constructor, which
initialises the rational to a value of zero.

The single-argument constructor is not declared as explicit, so there is an
implicit conversion from the underlying integer type to the rational type.

Finally, access to the internal representation of rationals is provided by
the two member functions numerator() and denominator().

It's in the section "Interface" near the bottom. BTW, I refer to the
numerator() and denominator() functionas as "access to the internal
representation". The reason for this is that a num/den representation has
some odd properties at the boundaries when used with a limited-precision
integer type. I am reserving the right to change the internal
representation. This gives rise to a question - is there any real-world need
to access the numerator or denominator of a rational number, in general?
(And if so, should there be a normalisation guarantee? At present the
results are normalised, but that's not necessary...)

I may look at rewording this section of the documentation. Any suggestions
would be gratefully received.


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