Re: Three simple questions

[Robert Dewar <robert_dewar@my-deja.com>]

In article <8sseq9$a2g1@news.cis.okstate.edu>,
  dstarner98@aasaa.ofe.org wrote:
> >It may be helpful to remember that the Ada RM has NOTHING to
> >say about how programs are represented. There is no necessary
>
> Then what does section 2.1 of the RM mean?


It is a VERY common misconception that 2.1 dictates
representation and suggests that the representaiton has
something to do with Standard.Character, but this is
just a "common sense" guess. This section merely says
that the compiler must be able to represent a certain
set of characters in the source, it has nothing whatsoever
to say about what representations are used.

For example, it would be quite fine to require keywords to
be written in bold in an environment where this made some
kind of sense (e.g. old style paper tape codes where Algol
keywords were typically marked as bold to distinguish them
from identifiers :-)

Whether it is a good idea or not depends on the environment.
I can certainly see an EBCDIC compiler using EBCDIC for source
representation even if type Standard.Character has to be ASCII,
but for most compilers in a typical environment, it makes sense
to choose a representation identical to Standard.Character.

It may well be the case in fact that you can use Text_IO to
read a source file, and get what you expect, but section 2.1
of the RM definitely does NOT guarantee this. Indeed it is
very clearly spelled out:

4   The character repertoire for the text of an Ada program
consists of the collection of characters called the Basic
Multilingual Plane (BMP) of the ISO 10646 Universal
Multiple-Octet Coded Character Set, plus a set of format_
effectors and, in comments only, a set of
other_control_functions; the coded representation for these
characters is implementation defined (it need not be
a representation defined within ISO-10646-1).




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