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From: mfb@mbunix.mitre.org (Michael F Brenner)
Subject: Re: Two ideas for the next Ada standard
Date: 1996/08/30
Message-ID: <506svr$h1v@linus.mitre.org>#1/1
X-Deja-AN: 177428050
references: <5009h5$ir4@netline-fddi.jpl.nasa.gov>
 <506ceh$25o4@info4.rus.uni-stuttgart.de>
organization: The MITRE Corporation, Bedford Mass.
newsgroups: comp.lang.ada
Date: 1996-08-30T00:00:00+00:00
List-Id: <comp.lang.ada>


In additions to these two ideas, we should consider two more:     

(1) Efficiencies required for systems programming:
(1a) Permit placing a variable at an absolute physical machine
address (as opposed to a gnat virtual address).
(1b) Correct the language design error that CHECKED conversion 
between signed and unsigned integers may overflow or raise constraint_error.
(1c) Add logical operations (AND, OR, etc.) on signed numbers.
(1d) Make software reuse through generics efficient by REQUIRING
all expressions that would have been static in a non-generic package
to remain static when the package is made generic. In Ada-95, 
you lose staticness all over, and, consequently, you lose compile
time computation of most expressions, when you make a package generic.
(1e) Mandate a compiler-independent way to identify a procedure as the
interrupt handler for a given interrupt number. 
(1f) Mandate a standardized way to identify that an INTERFACE
parameter is to be passed by reference.
(1g) Legalize a compiler-independent way to overlay two variables. 
This could be accomplished without offending non-system-programming
purists, who are rightfully concerned with the safety violation
implied by overlaid variables in two steps as follows. First, mandate
that unchecked_conversions generate no code, and recommend that
they be optimized away whenever the compiler detects the possibility 
of doing so. Second, in the tradition of searchable keywords like
SYSTEM, CLASS, and UNCHECKED_DEALLOCATION, use pragma OVERLAID to 
document the fact that a variable MUST be optimized away. Alternately,
just change the wording of the manual from making overlaid variables
erroneous to making them a safety concern that must be tested carefully.
(1h) A FAST, mandatory, standarized way to put a stream of bytes out to 
a file, with no intermediate packages or code between the
Ada call and the underlying file system WRITE and READ commands,
giving random access to standard_input and the same I/O speed as 
competing languages, which now requires compiler dependent code.

(2) Make packages into second-class objects; currently they are
third-class objects, forbidding arrays of packages and forbidding
passing packages as generic parameters; a second-class package
would permit passing non-generic packages as generic parameters, which
permit an easy-to-read, easy-to-implement, very efficient method of 
creating iterators with a single level of generics across a wide
set of data structures. 

(3) I suggest calling the next version 2kX, in honor of the year 2000 problem
which will be biting CALENDAR software whose date limitations arise in the
neighborhood of 1999 plus or minus a hundred year sliding window.