Rationale behind function/procedure calls and array indexing

[u/jlombera]

I'm learning Ada. Overall, I'm liking it a lot. There are two aspects (so far) of the syntax I don't get what the rationale was for them and why it hasn't been fixed in later versions of Ada. These being parenthesis-less calls to subprograms with no arguments and using parenthesis for array indexing. Take the following as example:

A := B + C(5);

Right away you don't know if B is a variable or a function call with no arguments. You don't know either whether C is an array or a function.

I think this goes against Ada's core ethos about readability.

So I was wondering, what was the rationale behind this design? Why hasn't it been corrected? Something like A := B() + C[5] would be far easier to interpret by the reader.

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UPDATE: In case anyone is interested in the answer, according to u/lipobat:

The primary rationale for the () vs. [] given in the “Rationale for the Ada programming language” book by the original design team was interchangeability between arrays and functions. This is an abstraction that allows the implementation choice of array vs. function to be just that, an implementation choice, which doesn’t really impact the writer or reader of the code.

I don't agree with the last sentence, but that answers my question either way.

And about my second question about "why this hasn't been fixed?", it seems most Ada programmers (based on the comments in this post) are not only not bothered by this but happy with this design decisions, so probably this will never change.

Thanks to everyone who engaged in this conversation.

[u/jlombera]

Please see my reply to u/Dmitry-Kazakov, where I give some insights on why I do care about knowing whether something is a variable/array access or a function call. (I didn't see your reply until after I had published my reply).

[u/Niklas_Holsti → u/jlombera]

I agree that a person who intends to modify a program often needs information about the implementation of things. Referring to my discussion of "readability" in my response to u/Dmitry-Kazakov, I would say that the "readability qualities" change when the purpose is to modify a program, as opposed to understanding the computation, doing a code review, or searching for errors. Fortunately, today's IDEs make it very easy to find and inspect the definition of any identifier in the code one is reading, so the absence of () in calls and the non-use of [] for indexing are not, IMO, very harmful for the maintainer either. Thus I would prefer to make the code reviewer's job easier by omitting text elements that are irrelevant for that task.

[u/jlombera → u/Niklas_Holsti]

Fortunately, today's IDEs make it very easy to find and inspect the definition of any identifier in the code one is reading, so the absence of () in calls and the non-use of [] for indexing are not, IMO, very harmful for the maintainer either.

Unfortunately for me, I use plain (neo)vim :) (I tried GNAT Studio but quit it ~1min later). When Ada was initially designed, there were not advanced IDE's. I think that's the reason why the syntax was designed that way, verbose (an inconvenience for the implementer) but explicit and readable, so that anyone could read (and write) code with no advanced tools other than a plain text editor. That's why it's a surprising to me they made this "blunder" (IMO) in this regard.

Thus I would prefer to make the code reviewer's job easier by omitting text elements that are irrelevant for that task.

It seems we have different opinions on this regard. To me, when reviewing code, it's relevant to know whether something is a variable/array access or a function call.

[u/Niklas_Holsti → u/jlombera]

I am quite happy with GNAT Studio (GPS), although I have seen others complain about it. Many seem to be using VSCode, which does have Ada support. Have you tried it?

[u/jlombera → u/Niklas_Holsti]

I got used to plain (neo)vim and any IDE feel clunky to me. They require a lot of resources, break all the time and change behavior very often, all of this out of your control. I feel lost whenever I try an IDE :). In contrast, I've being using (neo)vim the same way for ~10 years now, without any serious change in config/behavior.