Re: Beware: Rep spec on an enumeration type causes code explosion

[Ken Garlington <kennieg@nospam.flash.net>]

John G. Volan wrote:
> 
> Ken Garlington wrote:
> 
> > A response to this statement was: "There is no need for anything so
> > elaborate." The corresponding code did the conversion without a
> > check, which prompted me to ask how validity was handled.
> 
> Sorry, let me clarify: I wasn't commenting on the need to use 'Valid, of
> course that is quite necessary. What I was getting at was that you
> seemed to imply that the "holey" type ought to be something other than
> an enumeration type, let's say an integer type;

No, I was assuming a conversion between a holey to non-holey enumeration
type;

> and that the programmer
> should write some elaborate function involving perhaps a case statement
> to do a mapping between valid integer values and the target enumeration
> type.  

Maybe (although it shouldn't be that elaborate). I have seen cases where
using a case statement is slightly more efficient than using the
built-in
type conversion (as well as the opposite). Given the expected use to
convert
I/O, small optimizations in this area can be important. Of course, the
choice is compiler dependent.

> All I was trying to show was that Ada's built-in type conversion
> facility can "automagically" supply this mapping, if you simply derive a
> "holey" enumeration type from a parent "contiguous" enumeration type.
> 
> --
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