Re: Enumeration representation

[Stephen Leake <stephen_leake@acm.org>]

"Luke A. Guest" <laguest@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk> writes:

> Hi,
> 
> Am I correct in saying that enumerations don't necessarily begin at zero?

Hmm. Say you have:

type Enum is (One, Two, Three);

Enum'first is One (one definition of "begin" :).

Enum'Pos (Enum'first) is 0 (RM 3.5.1 (7) - first position number)

However, none of that says what is stored in RAM. If you specify a
representation clause:

for Enum_Type use 
  (One => 1,
   Two => 2,
   Three => 3);

Then One will be stored as 1 in RAM. The above values for 'first and
'pos are not changed.

> Is this implementation dependent?

In the absence of a representation clause, the representation in RAM
is technically implementation dependent, but it's extremely
likely to be the same as the position number.

-- 
-- Stephe