DIP 52 - Implicit conversions

[Don]

On Wednesday, 11 December 2013 at 21:00:19 UTC, Joseph Rushton 
Wakeling wrote:
> On 11/12/13 13:44, Simen Kjærås wrote:
>> I've tried to figure out good ways to add some sorely-needed 
>> implicit
>> conversions to the language, but I'm sure there are details 
>> that need to be
>> ironed out. In other words - destroy!
>
> Since you brought up std.complex: some of the issues here are 
> subtle.  For example, it's appropriate to allow implicit 
> conversion from numerical => Complex (although this can be done 
> fairly readily by just calling complex(x) where x is a 
> numerical type); it's also appropriate to allow implicit 
> conversion from Imaginary => Complex; but it'd be wrong to 
> allow implicit conversion from numerical => Imaginary.
>
> Conversely, I'm not certain whether it'd be appropriate to 
> allow implicit conversion Complex => numerical or Complex => 
> Imaginary, even if the imaginary or real parts respectively 
> were zero.

I don't think Imaginary should exist at all. Mathematically, it's 
nonsense.
It's exactly like defining a NegativeInteger. It has horrible 
properties, such as, it's not closed under multiplication!

I don't think there are many applications for pure imaginary 
numbers, I tried to come up with one but failed. Kahan only 
provides one example in his paper, and it's contrived. It 
eliminates one subtlety but introduces far more. In practice it 
is always far better to just operate directly on the real and 
imaginary parts.