Hi all,
I posted this a while ago in comp.lang.c++.moderated and didn't get
any responses and so I thought I would repost in this group.

My question is- to what extent are user-defined conversions used when
doing template function argument deduction.

 Page 14-38, 14.8.2 [temp.deduct], paragraph 10 states that-
"Conversions (4) will be performed on a function argument that
corresponds with a function parameter that contains only non-deducible
template parameters and explicitly specified template parameters.".

Does this mean that if argument deduction can't otherwise be done
(i.e. the function parameter contains only non-deducible template
parameters) then user-defined conversions will be tried to find a
deducible argument?

My particular concern is that I have a complex<double> array class in
which I want to distinguish between lvalue & rvalue usage when
subscripting. I therefore return a proxy class from the subscript
operator which has a conversion operator used when an rvalue is
needed. However, in Visual C++ 5.0 many library functions for complex
are template functions that take a complex<T> and when called with the
result of a subscripting operation, the proxy doesn't have its
conversion operator called and argument deduction fails. Is this just
a draft-non-conformance of VC 5.0?

Thanks,
Brian Parker (bparker@gil.com.au)
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