Re: Fixed-point question

[Patrick Noffke <patrick.noffke@gmail.com>]

On Saturday, June 27, 2015 at 3:42:11 PM UTC-5, Bob Duff wrote:
> > For C2, the compiler is looking for a visible "/" that yields a result of
> > Fixed_Type, and only Fixed_Type's "/" does that.
> 
> Well, fixed-point division is kind of magical.  The individual
> fixed-point types don't have a "/" that takes parameters of the type and
> returns the same type, but there's a "/" on universal_fixed that can be
> used on any fixed-point types, and the two operands and result can all
> be of different fixed-point types.  See 4.5.5(18).  Similar for "*".
> There are also mixed fixed-integer ops for each fixed-point type.
> 
> There's a rule somewhere that says the context has to provide
> the type of the result, so the compiler knows how much precision
> is needed.  E.g. you can say "X := Y * Z;" but not
> "X := Y * Z * W;".
> 

But for C2 why is the compiler implicitly converting N and D to universal_fixed before doing the division?  Isn't it just as valid to treat the constants as universal_real and use the root_real "/" operator first and then do the conversion?  I don't see this discussed in 8.6 (29).  There must be another rule for type conversion taking preference over division.

Thanks,
Patrick