Re: Ada and Automotive Industry

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Ken Tindall says

There's quite a lot in Ada that does indeed imply
bad performance. Quite a few optimization techniques
are disallowed because of the elaboration and
evaluation rules (see papers by Mike Kamrad for
examples).

  General claims like this are often bogus, and
  this one is. Please state one specific claim,
  it is impossible to refute incorrect generalities!

You still miss the point. If Ada implementations costs
20% more code space then that's a few cents per unit.
But a few cents per unit added up over millions of
units adds up to a lot of money.

  Please prove your point that Ada implementations
  cost 20% mode code space. Some Ada implementations
  may be more expensive than some C implementations,
  and the converse is also true (for example there
  are lots of C compilers for the PC that generate
  far worse code than GNAT). But there is no basis
  at all for such general claims.

It's not a red herring. Ada is hugely complex, and not
well understood. If you think that Ada is elegant and
consistent then you don't understand it very well. You
only have to look at the "Dear Ada" column in ACM
Ada Letters to see this (I really recommend you do
read the column!).

  Almost any language has complex edges in it. But one
  interesting thing about Ada is that these usually take
  the form of whether some marginal diction is or is not
  legal, NOT, as in C, the case where something that looks
  obvious is legal but does something quite different.

  Also remember that complexity in terms of features in
  a language can result in improved simplicity in a
  program. This general claim of excessive complexity
  in Ada is almost always made by those who do not
  know Ada very well. Parnas publically made these
  claims, and I challenged him to a debate on the
  issue, which he accepted, but unfortunately backed
  out due to ill health at the last moment, and despite
  my invitation, never rescheduled. A pity ...

Tony Hoare once said that one of the keys to success in language
design was to make it so simple that there are obviously no
deficiencies. The other way is to make it so complicated that
there are no obvious deficiencies.

  Be careful using Tony Hoare as your ally, check what he
  would think of your proposed alternatives to Ada before
  assuming that he would agree with your position! In fact
  he considers Ada to be considerably superior to much of
  the competition.

It is impossible. Ada 83 tasking cannot be used reliably for real-time
(as the Boeing people above mentioned). Ada 95 tasking still leaves a big
efficiency problem, which is crucial to the automotive industry,
where a few cents on a control unit add up to millions over a product
life.

  Again, unsubstantiated general claims. It must almost certainly be
  the case that the writer does NOT know Ada very well. If I am wrong
  on this, then Ken, make some specific technical points that we can
  address instead of unsubstantiated generalities.