Re: Ada to Ada Translator ?

[Optikos <optikos@verizon.net>]

On Tuesday, May 21, 2019 at 5:15:54 PM UTC-5, Randy Brukardt wrote:
> "Optikos" wrote in message 
> news:a8d0f6ca-d5cf-4831-8803-9c1bb6198116@googlegroups.com...
> >On Monday, May 20, 2019 at 6:19:55 PM UTC-5, Randy Brukardt wrote:
> >> "Optikos" wrote in message
> >> news:64883feb-3e49-4c6a-855c-6673068e970c@googlegroups.com...
> >> ...
> >> >Conversely, if you utilize Yacc & Flex, it would be LR(k) bottom-up 
> >> >parser,
> >> >which would be an admirable accomplishment in its own right.
> >>
> >> Why? There are a number of such grammars out there, and Janus/Ada was
> >> designed from the beginning (in 1980!) using an LALR parser. (That was a
> >> requirement of the class project at the University of Wisconsin that 
> >> formed
> >> the basis of Janus/Ada, and we discovered that switching was impractical 
> >> as
> >> an LL parser was going to be several times larger than the 48K RAM 
> >> available
> >> on CP/M-80. With some clever storage, we got the LR tables to fit with 
> >> space
> >> to spare.)
> >
> >I said "admirable", not unique.  I was speaking in the context of an 
> >open-source
> >Ada language-translator, not a closed-source one.
> 
> Which is relevant how?

Patrick's entire thread here is about an •open•-source tool that he is proposing.  Relevant means related to the matter at hand.

> There are (or at least were) a number of YACC 
> grammars for Ada floating around the web. And there's no difficulty in using 
> them...

Aren't all the “number of YACC grammars for Ada floating around on the web” rather out-of-date for only Ada83 or Ada95?  If Patrick is proposing a tool that is capable of parsing Ada2005 or Ada2012 or Ada2020, then modernizing those out-of-date yacc grammars to the current era is of some degree of difficulty.  Doing so in an open-source project would be some degree of laudable accomplishment, as some degree of incremental advancement.  (Even better if the modern-Ada Yacc grammar in the open source project were licensed with an MIT-esque permissive license instead of GPL, since GNAT and ELPA ada-mode for Emacs are both GPL-licensed.)

Furthermore, Patrick is effectively proposing something further:  parsing not merely bland modern Ada straight from the ISO standards, but also every GNAT extension so that his Ada-to-Ada code-generator is a drop-in front-end wrapping GNAT.  I am fairly certain that absolutely no extant open-source Yacc grammar for Ada has all the GNAT extensions (as well as parsing modern Ada2005 or Ada2012 or Ada2020).  I reiterate:  Such an open-source Yacc grammar comprehensive of all variants of Ada (so that it could be a completely transparent front-end to GNAT) “would be an admirable accomplishment in its own right” as I originally stated.