yank unary '+'?

[Walter Bright]

Don wrote:
> Walter Bright wrote:
>> 3. used with operator overloading to convert a user defined type to 
>> its preferred arithmetic representation (a cast can't know what the 
>> 'preferred' type is)
>  > 5. to coerce default integral promotion rules (again, cast(int) won't
>  > always produce the same result)
> 
> This one is interesting, and might be the strongest argument, but I 
> don't understand it. An example would be interesting.

Integral promotion rules:

byte b;
+b => int

dchar dc;
+dc => uint

long l;
+l => long
cast(int)l => Oops! lost some bits

user defined type:

struct S
{
     long opCast() { ... }
     S opAdd(ref S) { ... }
}

S s;
+s => long result
s + s => S result
s + +s => long result
s + cast(int)s => Oops! lost some bits!