Re: An observation of Ada (may offend)

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <3kr20s$gqq@gnat.cs.nyu.edu> dewar@cs.nyu.edu (Robert Dewar) writes:

  > Regarding the suggestion:  pragma Restrictions(No_Unspecified_Child_Units)

  > Presumably the right form of this pragma is

  >   Pragma Child_UNits (unit, unit, unit);

  > with the meaning that only the named units would be allowed as children.
  > This is a perfectly legitimate pragma, and one that could be implemented.

    This actually is an improvement to my suggestion, and one I
recommend to all Ada implementors.  (In fact, if Robert Dewar doesn't
get around to adding it to GNAT, I may send it to him.)

    Of course, and the reason for posting this, is that one needed
form of the pragma is "pragma Child_Units(None);" or "pragma Child_Units;"
I perfer the second form, what do the rest of you think?

    I guess there is a third form--to deal with the special case of a
child unit named None, you might want to use a reserved keyword here.
How about "pragma Child_Units(NOT);"?

  > But I wonder about this whole concern. After all you can always go and
  > edit out the "abs" of Norm's abs private, or add to the list of child
  > units in the above pragma.

   The point is that the software maintainer can look at the source
file and know what child units exist, not that implementers are
forbidden to add them.  If most people agree with the suggested
syntax, I will start using pragma Child_Units without any compiler
support.  (And probably quickly add the support...)

  > The language can't do everything here!

   Right, this is and should be a voluntary annotation in most
environments.  But I expect that if support is forthcoming, the
safety critical people will not only use it, their coding standards
will insist on it.

--

					Robert I. Eachus

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