friend operators

[Bernd Speiser]

Hi,
I´m still using gcc 2.95.3 on a SuSE Linux 7.3 system.

I´m trying to write some C++ code which uses operator overloading in a
friend situation. Also this is within a template (but I have already
observed all requirements pointed to in the FAQ, so this is ok, and the
problem also appears in non-template classes).

When I have a declaration like

friend ostream & operator<< (ostream &, VariableQuantity<U, D> &);

and I declare later another operator<< with different argument types,
e.g.

void operator<< (string &);

this does not work if the second operator<< is NOT a friend.
Then I get the error message

../Quantity/Quantity.h: In instantiation of `Quantities::VariableQuantity<Units:
:QuantityUnit<Quantities::LengthUnitClass>,Dimensions::QuantityDimension<Quantit
ies::LengthDimensionClass> >':
Length.h:431:   instantiated from here
../Quantity/Quantity.h:852: invalid use of undefined type `class Quantities::Var
iableQuantity<Units::QuantityUnit<Quantities::LengthUnitClass>,Dimensions::Quant
ityDimension<Quantities::LengthDimensionClass> >'
../Quantity/Quantity.h:907: forward declaration of `class Quantities::VariableQu
antity<Units::QuantityUnit<Quantities::LengthUnitClass>,Dimensions::QuantityDime
nsion<Quantities::LengthDimensionClass> >'
../Quantity/Quantity.h:852: confused by earlier errors, bailing out

when I try to instantiate the template (or, if this is not a template class, if
I just want to use the class).
If the second operator<< is also a friend, it compiles ok.

Is there something illegal about my code?

Thanks for any help.
Bernd
-- 
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Bernd Speiser
Institut f"ur Organische Chemie
Auf der Morgenstelle 18
D-72076 T"ubingen
Germany
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e-mail: bernd.speiser@uni-tuebingen.de
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