D (was: Quo vadis, GPC?)

[Rugxulo]

Hi,

On 7/30/10, Frank Heckenbach <ih8mj at fjf.gnu.de> wrote:
> Rugxulo wrote:
>
>> Frank, I would be curious what you think of Ada or Modula-2, esp.
>> since both of those have (official or unofficial) GCC support. And
>> there are already (weak) converters from Pascal to Ada, Oberon,
>> Modula-2, etc. (But no GNU Oberon, only OO2C.)
>
> Since you ask me specifically: I've never programmed in any of those
> languages myself (outside of University), and I haven't followed
> their development in recent years.

Well, I only ask you because you brought all this up!  ;-)  Note that
I don't know any of those languages myself, but they are mostly
Wirth-ian like Pascal.

> Since most of these languages are not widely used, I wouldn't
> consider them attractive targets for a converter.

Maybe not individually, but taken as a whole, all the Wirth-ian
languages and their users can add up. And it seems many users use (or
have used) more than one (except me, so far).

> Ada may be an
> exception, but it's still less widely used than C++, and at least I
> know C++ much better than Ada -- though if there's a number of Ada
> programmers here (whom I don't know yet :-) it might make it
> interesting to consider as a target.

Well, Ada has been folded into the GCC tree since 3.2 or so. Even
DJGPP supports it. No, it's not got huge support, but people do indeed
use it. Honestly, I'm surprised (but glad) GCC still supports it.
Perhaps they have lots of DoD volunteers, I dunno.  ;-)   Originally
the DoD paid a lot to have it written, so I guess that didn't hurt
either.

Note that GNU Modula-2 (EDIT: I've never tried) partially requires C++
(I think) to build due to exceptions. They are allegedly very mature
now but development does focus on Linux (surprise surprise) with some
lesser testing on Cygwin and Mac OS X.

I'm not sure what to think, I have mixed feelings. I'm glad for them,
but I wonder why all these efforts have to take place separately and
not cooperate more. Wirth's children should stick together.  ;-)

> Weak converters are IMHO of not much use, since turning them into
> full converters is probably as difficult, if not more so, than
> writing one from scratch. (Furthermore, I suspect they each support
> only one Pascal dialect, in contrast to GPC.)

Correct, and e.g. P2Ada didn't work for my simple program. I'm not
saying a rewrite is bad (or even feasible), just saying that some
effort had already been done. Maybe there's some reusable code or good
ideas at least, I dunno. But this seems more of something for you
(expert) to decide than me (noob).  ;-)

> As an example, the GPC frontend was originally derived from the C
> frontend (note, I'm not talking about the backend issues here, but
> the actual frontend responsible for handling Pascal). Initially,
> this provided some success quickly, as many Pascal features map more
> or less roughly to C features (e.g. arrays to arrays, [variant]
> records to structs/unions, for/while/repeat loops to for/while/do
> loops, Integer to int, mod to %, procedures/functions to functions
> etc.). But the devil is in the details, and that's a damn big devil
> here

I'm not knocking your decision, it worked quite well! GPC is a nice
product, nicer than most software. I don't personally believe software
is throwaway, so I do think it should be reused or preserved (if
possible). However, I do understand hindsight. Even RMS complains that
choosing Mach for Hurd was meant to save them time but probably hurt
in the long run. Yes, ironically, sometimes it is easier to rewrite
from scratch. But you need experience, and that usually only comes
from modifying a pre-existing project.