Speaking as someone who left a company that did radar software development in AD...

PeCaN · on April 27, 2016

> It reminds me a bit of GO with its packages.

Ada Tasks also bear some semblance to goroutines. (In the sense that they share memory by communicating instead of communicating by sharing memory.)

It's definitely a nice and well-designed language IMO—with a share of annoyances[1] and flaws—but overall deserving of more attention than it gets. Lately I've gotten comfortable enough with it that I have been making a habit of reaching for Ada for side-projects where I would formerly use C. (For example, I'm writing a toy X window manager in Ada at the moment—using XCB from Ada is a little ugly at times but definitely bearable.)

1. For example, why can't a record discriminant be a range bound? Answer: standards committee didn't think people would use it. Of course, this means if you have an array of discriminated size, you can't conveniently have a type for a position in it. e.g.

  type Thing_Stack (Max_Size : Positive) is record
    Elements : array (Positive range 1 .. Max_Size) of Thing;
    Top_Index : Positive range 0 .. Max_Size := 0;  -- 0 = Empty stack
  end record;

Fails to compile with "Discriminant cannot constrain scalar type". According to [2], this is because

> This restriction is left over from Ada 83 (RM83 3.7.1(6)). We considered removing this restriction in Ada 95, but ultimately decided that the implementation effort to support this modest extension would outweigh the (more?) modest benefits. Perhaps a short-sighted decision, in retrospect...

> As for why the original Ada 83 restriction existed, noone knows for sure, but it probably relates to the historical purpose of discriminants as only for controlling the "shape" of the record, rather than being seen (as in Ada 95) as more general type "parameters."

And apparently it got left in Ada 2012 also.

(For C people, this is basically:

  typedef struct {
    size_t max_size, top_index;
    thing elements[];
  } thing_stack;

but bounds-checked and without the annoyance of allocating flexible array members.)

2. http://computer-programming-forum.com/44-ada/82b646ab38d529a...

acomjean · on April 27, 2016

Its been a while

I liked the records in ada. You could control the position and size of each field (which was really usefully for dealing with in binary messages) We had a ton of constrained types.

If I remember we has assert 'size on some of the records to make sure type changes didn't cause some records to become unexpected sized in case the types that made up the record changed.

variant records were fun, but when you start trying to do much (array of variant records?) it fell down.

The string handling left a little to be desired though..

atombender · on April 27, 2016

> It reminds me a bit of GO with its packages.

Not that alien a comparison, since Ada and Go both descend from Niklaus Wirth's languages. Ada was directly based on Pascal, whereas Go (and its precursors) is strongly influenced by Modula and Oberon, themselves successors to Pascal. Aside from some superficial syntax differences, Go looks a lot like Modula and Oberon.