[Info-vax] Access to _all_ VMS system services and library functions from DCL ?

[Stephen Hoffman]

On 2017-07-11 17:29:11 +0000, Simon Clubley said:

> On 2017-07-11, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
>> 
>> If the block is opaque to the end user ? similar to how BASIC tends to 
>> treat descriptors, scaled up to cover the system service data returned 
>> by itemlists  ? it'll work very close to what David is considering.     
>> Add in the ability to delay accessing the underlying data until its 
>> requested by the user and the storage and performance details are far 
>> less egregious than fetching everything.
> 
> Unfortunately, I got the distinct impression that David and others were 
> looking for something similar to a giant struct to be returned without 
> any layers of abstraction and for the variables within the struct to be 
> directly accessible by the application.

Oh, I well realize what some of the folks are looking for, and what 
they're familiar with.   I've written and maintained code in BASIC for 
far too many years, and am familiar with maintaining large-scale 
projects written in that language.

>> Yes, there's overhead on message-passing designs such as where David is 
>> headed here, but there's overhead in writing and processing itemlists 
>> too.   Trade-offs can change over time, and the holes in the existing 
>> OpenVMS design ? from back when memory was tight and processor  
>> performance was lacking ? are quite apparent.
> 
> I've never seen David advocate for message-passing and OO designs before.
> David tends to advocate for a very different style of coding.

David is a longstanding proponent of string descriptors and itemlists.  
 In various ways, extending what descriptors and itemlists provide 
leads more or less directly into what OO can provide.  OO generalizes 
that older model a bit, and adds more, and makes some parts of the API 
opaque.   Much like string descriptors in BASIC.   Would moving to OO 
be a stretch for some folks?  Sure.   I think many will adopt it, once 
they see how it works, and how well it works.   There's unfortunately 
no good path forward from the era of descriptors-and-itemlists APIs, 
and incremental updates just isn't going to provide a particular coding 
advantage and any particular draw.

Unfortunately, moving from descriptors-and-itemlists to OO is a chunk 
of compiler and API work, so it's not likely happening soon on OpenVMS.


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