:From Erik-wikstrom@telia.com Thu Dec 27 15:20:33 2007
:On 2007-12-27 21:14, Thelma Lubkin wrote:
:> matrixd.cc:244: warning: passing `const Octonion<double>' as `this'
:> argument of
:> `Octonion<scalar> Octonion<scalar>:perator*(const
:> Octonion<scalar>&) [with
:> scalar = double]' discards qualifiers
:>
:> I seem to get valid results if I ignore the warning, but I'd like to
:> understand what it means and to modify my classes so that it no longer
:> occurs.

:I am not quite sure (so I ought to not say anything) but have you
:declared the * operator as const? E.g.:

:template<class scalar>
:class Octonion : public Vector
:{
: // ...
: Octonion<scalar> operator*(const> Octonion<scalar>&) const;
: // ...
:};

:Your code would probably not compiler if you had not, but who knows.

I have the const on the argument, but not on the operator. It
does, however both compile and run.

--thelma
--
:Erik Wikström

On 2007-12-28 05:46, Thelma Roslyn Lubkin wrote:
> :From Erik-wikstrom@telia.com Thu Dec 27 15:20:33 2007
> :On 2007-12-27 21:14, Thelma Lubkin wrote:
> :> matrixd.cc:244: warning: passing `const Octonion<double>' as `this'
> :> argument of
> :> `Octonion<scalar> Octonion<scalar>:perator*(const
> :> Octonion<scalar>&) [with
> :> scalar = double]' discards qualifiers
> :>
> :> I seem to get valid results if I ignore the warning, but I'd like to
> :> understand what it means and to modify my classes so that it no longer
> :> occurs.
>
> :I am not quite sure (so I ought to not say anything) but have you
> :declared the * operator as const? E.g.:
>
> :template<class scalar>
> :class Octonion : public Vector
> :{
> : // ...
> : Octonion<scalar> operator*(const> Octonion<scalar>&) const;
> : // ...
> :};
>
> :Your code would probably not compiler if you had not, but who knows.
>
> I have the const on the argument, but not on the operator. It
> does, however both compile and run.

If we simplify the problematic code as much as possible, does it look
like this:

const Octonion<double> a;
Octonion b;
a * b;

i.e. you have a const Octonion which you try to multiply with a
(possibly) non-const Octonion. If that is the case you must make the
operator const too.

--
Erik Wikström