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Newsgroups: comp.lang.ada
Date: Tue, 19 Jun 2018 15:17:52 -0700 (PDT)
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Subject: Re: Why are Ada compilers difficult to write ?
From: Lucretia <laguest9000@googlemail.com>
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Xref: reader02.eternal-september.org comp.lang.ada:53178
Date: 2018-06-19T15:17:52-07:00
List-Id: <comp.lang.ada>

On Tuesday, 19 June 2018 22:33:38 UTC+1, Vincent  wrote:
> Dear Ada programers,
>=20
> I have often heard that Ada compilers where expensive because they are ve=
ry difficult to write, compared to Pascal or C ones. So my question is : wh=
at in the Ada language poses problem to a compiler ? What are the challenge=
s ? Where can I find documentation about that ?

Here are the issues I see:

1) Getting the grammar from the AARM correct, because it's highly ambiguous=
, doesn't include the pragmas (still!!!!) in the correct places and that it=
 includes semantic info, especially for ID's.

2) There are many many many rules that have to be observed *and* documented=
 for each implementation.

3) Overload resolution, as Jacob mentioned, it apparently a bitch.

4) It's a big language, including abstracted threaded via tasks, protected =
objects, so it's not as simple as just writing a Pascal subset.

Pascal as originally designed is tiny and can be implemented within a few d=
ays to a week. TBH I think I could knock up a Pascal scanner and parser in =
an afternoon, that's half of it done, stick it onto LLVM and it yer done.

C is a massive bag of shit and would take ages to write a *decent* compiler=
 for, it has soooooooooooooooooooooooo many edge cases because it's such a =
mess. Even though, all it is, is a simple list of declarations (variable, c=
onstant, functions "prototypes"), function "bodies" and "types," but it's e=
verything else that's the problem with C.