No more implicit conversion real->complex?!

[kris]

Don Clugston wrote:
> Norbert Nemec wrote:
> 
>> I just notice that as of D 0.150, implicit conversion from
>> real/imaginary to complex does not work any more. I could not make out
>> the message containing the suggestion by Don Clugston, so I'm not sure
>> about the rationale.
>>
>> In any case: if this conversion does not work implicitely any more, I
>> wonder whether I understand the rule which conversions do? real->complex
>> is possible without ambiguities or loss of information. Why not make it
>> implicit?
> 
> 
> It's not 100% unambiguous, there are two possible conversions
>     7.2 -> 7.2 + 0i
> and 7.2 -> 7.2 - 0i.
> 
> OK, it's not a big deal. But the real problem is that with that implicit 
> conversion in place, overload resolution is a real nuisance.
> 
> Consider
> creal sin(creal c);
> real sin(real x);
> 
> writefln( sin(3.2) );
> 
> Now, 3.2 is a double, so it tries to find sin(double).
> This fails, so it tries implicit conversions.
> Both sin(creal) and sin(real) are possible, so it's ambiguous, and
> compilation will fail.
> Up to now, the only way of overcoming this was to supply seperate 
> functions for float, double, real, and creal arguments. This is clumsy, 
> and becomes impractical once multiple arguments are used.
> 
>> I think this is an important issue: in numerics, mixing of real and
>> complex values happens all the time, therefore it should be as simple as
>> possible.
> 
> 
> I agree. But the implicit conversions were actually making mixing of 
> real and complex functions much more difficult. It would be good to have 
> someone other than me seriously thinking about these issues, and gaining 
> some experience with numerics in D.
> 

By this argument, if the overloaded types were char and long (instead of 
creal & real) then D should not allow implicit conversion there?