Re: Early Ada Mistakes (was: Re: += in ada)

[Marin David Condic <nobody@noplace.com>]

Yea, there was the "Pascal-Like Subset" that was a starting point for a 
lot of vendors, but a) it wasn't any kind of approved, validated 
standard, so you couldn't be sure of any kind of portability (every 
vendor had their own rules about what they were going to implement) and 
b) there were things that had to be included that were way off of the 
standard in order to make it work. The most obvious was Text_IO: You 
couldn't do I/O for anything except text (numeric types, enumerations, 
etc.) without generic instantiation and, as you observed, that was the 
"Level 2" part. So compilers had to come up with some sort of hack-job 
to give you I/O for floats, integers, etc., without having generics. 
Double-Plus-Ungood for developing anything you hoped to make portable.

I realize it all got fixed eventually, but it *did* leave a bad taste in 
  the mouths of a lot of users. Ada was supposed to be this wonderful 
language that was going to be portable across all machines and all 
compilers - but the wonderful parts were not there and the portability 
was no better - perhaps worse - than your average Fortran or C compiler. 
Disillusionment followed rapidly.

Even today, I think there might be some food-value in a "standard" 
subset that would be aimed at small embedded machines. (Assuming anyone 
wants to try to venture into that market again.) Spark might make a nice 
start - except that it isn't a "Standard". I don't know enough about 
Spark to know if it limits itself to things that would hack the language 
down to something easily targeted to small embedded machines. It just 
might be valuable to have something that could easily fit a small target.

MDC



Robert I. Eachus wrote:
> 
> There were actually two, pretty well understood by all compiler 
> developers.  The first was the Pascal subset, this was basically 
> everything in Ada that was also in Pascal.  A lot of compiler developers 
> either modified a Pascal compiler to compile this subset, or built a 
> tool to convert from the Pascal subset of Ada into Pascal.
> 
> The next step up was the Pascal superset.  This was basically everything 
> in Ada except chapters 9 (Tasking), 12 (Generics) and most of 13.  This 
> was the language that most compiler developers used--and possibly still 
> do--to implement the Ada run-time.  Of course, a lot of people would say 
> that some compilers, such as the original Telesoft compiler were only 
> useable with the Pascal superset.  I am not one of them.  I never found 
> the original Telesoft compiler useable.  But then again, maybe I never 
> found the right Pascal subset to use with it.
> 


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Marin David Condic
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