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

[dmarshal@netcom.com (David Marshall)]

gwinn@res.ray.com (Joe Gwinn) writes:

[interesting information on Ada95 code tuning snipped]

>We have now removed the bulk of the rep specs on enumeration types, just
>trusting for now that the compiler will always start enumerations at zero,
>just like C/C++.  Ada95 does not specify the base value of an enumeration,
>so compilers vary. We were using rep specs to govern the representation of
>Ada records used to generate and understand messages exchanged with
>display consoles coded in C++.  This idiom is used extensively.   For
>portability, we will eventually change the code to remove all ungoverned
>enumerations.

Just a moment!  Ada95 DOES represent the base value of the first
enumeral as zero, unless otherwise specified with an enumeration
representation clause.

RM95 3.5.1(7):

Each enumeration literal corresponds to a distinct value of the
enumeration type, and to a distinct position number.  The position
number of the value of the first listed enumeration literal is zero;
the position number of the value of each subsequent enumeration
literal is one more than that of its predecessor in the list.

RM95 13.4(8):

For nonboolean enumeration types, if the coding is not specified for
the type, then for each value of the type, the internal code shall be
equal to its position number.
-- 
Dave Marshall
dmarshal@netcom.com