Re: Not intended for use in medical,

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

Matthew said

  <<I stand corrected.  From what I've read, however, that language has been
  lamtive to Ada.

 of its too-frequent use of automatic type coercions.
  Opinion?>>

A good example of reading other people's ill-informed assessments. If you see
someone say this about Algol-68, it means they don't know much about Algol-68,
or, more likely, in an attempt to impress their friends and neighbours they
are quoting opinions which they do not understand. I am willing to bet that
Matthew is quite unaware of what type coercions mean in Algol-68. For
example

      a := b;

where a and b are integer variables, is considered a type conversion (mode
coercion) in Algol-68, since the right side must be converted from ref int
to int by dereferencing -- gosh isn't it awful a language having automatic
type conversions like that (note that Bliss actually agrees in this case,
but it is unusual in its opinion).

Do NOT assume that famous people know what they are talking about when it
comes to programming languages. Many well known people in the field break
my rule about not criticizing languages without having written a substantial
amount of code -- and they break it spectacularly, often criticizing features
that just don't exist.

A few years ago, I reviewed a proposal from some Canadian Professor which
dismissed Algol-68 on the silly grounds that Matthew mentions above (too
may type coercions), and gave as an example the following

   where a is ref ref int

   a := 4;

   is terrible, because it automatically deferences a and therefore you
   don't know what variable is being assigned.

There is only one problem with this. Algol-68 has NEVER allowed automatic
cooercion on the left side of an assignment, so the above is illegal
(you have to write an explicit conversion, analogous to the use of .all
in Ada, or * in C)

An irony is that I know exactly where he got this from, there is a well
known paper by a very well known author, who is considered an expert
in programming languages, which presents EXACTLY this wrong example.

Needless to say, I gave the proposal a very low rating, anyone who simply
adopts other people's opinion uncritically as their own is unlikely to
make a good scientific investigator!

  <<Do you disagree with the argument that a language is "bad" - specifically,
  Ada - if it's difficult to implement a compiler for it?>>

As I noted previously, writing any compiler is hard. Writing a good
compiler for C is difficult. If you think this means that a language is
bad, then all languages are bad. Yes, it is true that modern languages
like C++, Fortran-90, OO COBOL, and Ada 95 are harder to compile, but
so what. That's what computers are for -- doing work that we would have
to do ourselves otherwise. These comprehensive languages do a lot for
us that we would have to do for ourselves 

  <<Do you disagree with Les Hatten who said that Ada shouldn't be used,
   because it has a "large number" of interpretation requests?>>

Of course I disagree, Les Hatten does not know what he is talking about.
In fact the extent to which the standard has needed interpreting is
very small. Almost all of the AI's for Ada 83, all of which are resolved
for Ada 95, are for marginal issues that affect few or no programmers.
Furthermore, other languages if anything have MORE interpretations that
have to be issued (I wonder if Les has for example read the JOD for COBOL)

  <<Do you disagree with Tony Hoare's assessment that Ada should not be used
   for systems where high reliability is required?>>

This is not necessarily Tony Hoare's assessment today, and if you read his 
Turing award lecture carefully , you will find it is not so absolute. In
particular, he specifically notes that a subset of Ada *would* be a suitable
vehicle. Since all high reliability systems using Ada do in fact use a well
chosen subset, I see no conflict here. Indeed when I talked with Tony some
years ago, he expressed frustration that his lecture had been taken as 
condemning Ada out of hand. He was simply using it as an example of some
trends in language design to be worried about, and he felt that people
had misread the talk if they felt it was wholly negative to Ada.