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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: ada -> C translator
Date: 1997/04/09
Message-ID: <dewar.860582947@merv>#1/1
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References: <33436B29.41C6@sema-grenoble.fr> <E833ux.337@world.std.com>
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Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-04-09T00:00:00+00:00
List-Id: <comp.lang.ada>


Fergus said

<<There is a trade-off between efficiency, portability, and simplicity.
The approach I'm talking about is certainly feasible for Mercury:
we have an existence proof.  Ada is more complicated than Mercury,
and it may have more features that don't map nicely into C,
but it's not _that_ much more complicated, so I remain unconvinced
by claims that this sort of approach would be infeasible.

>For example, what shall we do with exceptions in C?

I implemented exceptions for Mercury without much difficulty;
it took about a day.  (The reason it was so easy was that the
mechanism needed is similar to that needed for backtracking,>>


You may remain unconvinced, but it just goes to show that you have not
really looked at the detailed issues of implementing Ada this way.
Obviously Mercury has *much* simpler compilation semantics than Ada
if it can be handled in this way -- that's entirely possible certainly.

Also, it becomes clear that what you have in mind for an Ada compiler
written this way is more of a small subset Ada toy than a real compiler
(it is out of the question for example, for a real Ada compiler, which
must implement pragma Import and pragma Export properly to consider not
using an invocation stack).

I think you are trying to solve a much simpler problem with Mercury 
(certainly sounds much simpler from all your descriptions), and you
assume that this experience can be projected on to Ada, it cannot!