[Info-vax] VSI Basic

[Craig A. Berry]

On 3/1/23 7:57 PM, Arne Vajhøj wrote:
> On 3/1/2023 8:48 PM, Craig A. Berry wrote:
>> On 3/1/23 5:44 PM, Arne Vajhøj wrote:
>>> Based on comp.os.vms questions and forum.vmssoftware.com questions,
>>> then VMS Basic seems to be pretty widely used on VMS.
>>>
>>> I don't think VMS Basic is at risk to be deemed financially
>>> not worth it.
>>>
>>> It just has to be completed. I suspect that the main reason
>>> why Fortran was done before Basic was the simple fact that
>>> LLVM has Fortran support (flang) out of the box. Alternative
>>> explanation is that VMS Basic has some advanced features while
>>> Fortran is probably more traditional.
>>
>> The Fortran compiler just released is based on the existing front end
>> and the G2L translation layer that produces LLVM intermediate
>> representations out of GEM intermediate representations.[1]  This has
>> been stated publicly a number of times, as has been the fact they are
>> going roughly in order by number of affected customers as they move
>> through the list of compilers.  flang has nothing to do with it.
>>
>> A different project to port flang to VMS and add enough VMSisms to make
>> it mostly compatible with the existing VMS compiler is theoretically
>> possible, and somewhat interesting for newer features and standards
>> compliance.  I believe it's been floated in the newsgroup before.  It
>> seems unlikely anyone has the will or the resources to do it near-term.
> 
> I was not implying that the released Fortran was flang - I know it
> is not.
> 
> My speculation was that because flang frontend exist, then the LLVM
> backend has everything needed to support Fortran language readily
> available making it easier to get the VMS Fortran frontend working.
> 
>> The only other possibly relevant note about which of these two compilers
>> gets done first is that the implementation of COMMON blocks in Fortran
>> appears not to have been as evil as the implementation of MAP blocks in
>> BASIC, which affects what has to be done to G2L and/or the front end
>> itself to get things working.  In the case of BASIC, it sounds like
>> reimplementing MAP in the front end is going to be less trouble than
>> hacking G2L to manage what BASIC does.  Again, the fact that Fortran
>> could be built with less intrusive changes to G2L has nothing at all to
>> do with flang.
> 
> See above. And compare to Basic where there is no "blang"
> and if something is missing in the backend then it may be
> easier to hack the frontend than the backend.
> 
> But then I don't know LLVM at all. So I am just speculating.

Yeah, me too, but my understanding is that the gotchas are in language
implementation details, not language features.