[Info-vax] Programming languages on VMS

[Jan-Erik Soderholm]

Den 2018-02-09 kl. 13:21, skrev Johnny Billquist:
> On 2018-02-09 13:10, hb wrote:
>> On 02/09/2018 12:06 PM, Johnny Billquist wrote:
>>> First of all, having the file versions are much more lightweight when
>>> you want to go back and check something from a previous version, than to
>>> go through the backup system and restore a previous version, not to
>>> mention the simple ability of being able to compare them side to side
>>> without having to start doing renames or other tricks so that the
>>> restored version from the backup don't actually overwrite the current
>>> version with the same name.
>>>
>>> Second, I'm not aware of any backup system that does a snapshot at every
>>> file close. The closest to what you describe that I know of is the Time
>>> Machine from Apple. But that only takes a snapshot every hour. I can
>>> create many versions in one hour when I'm developing code.
>>>
>>> And there is still that issue of having to go into the time machine
>>> interface and restore if I want to get an older version back, and of
>>> course the name collision if I also want to retain the current version,
>>> and maybe also want to make comparisons or checks against 7 other recent
>>> versions in short order.
>>>
>>> But hey, I certainly do recognize that I'm not a typical user, and my
>>> patterns are probably both odd and archaic. I don't really believe in
>>> IDEs either, but I do believe in version control systems. But I do not
>>> consider version control systems to really overlap my use of file
>>> versions either.
>>
>> IDEs like Eclipse have a local history, besides a plugin for the version
>> control system of your choice. The local file versions are identified by
>> the time, when the source was saved, not by a number. You can do
>> compares within the IDE, local history and/or any revision in your
>> version control system. Just a few mouse clicks. If you want, you can
>> merge the code from the compare window/view, difference by difference
>> with another mouse click. Fits me.
> 
> Which just tells me that others also find similar usercases to mine, but 
> since the IDEs are designed for systems that don't have file versions, they 
> instead have to implement the same thing locally inside the IDE to 
> accomplish the same thing.
> 
> Obviously then, more people don't consider backups or version control 
> systems to provide the same capability or cover the same use case that the 
> file versions do.
> 
> Isn't it good to be on a system where this need was covered already at the 
> OS, and not becomes a specific functionality located just inside each tool?
> 
>    Johnny
> 

I do not see "backup" and "file versioning" as two features/tools that
replaces one of the other. They are complements.

We have backups, of course. Including all versions. And if someone
happens to do a PURGE, we have 60 days to recover the files from
the backup. Any deleted files, included purged versions, are marked
as "Inactive" and are retained for a configurable time frame, right
now it is 60 days. To get a full copy of the actual state (at least
from the night before), one just retrive the default state "Active".

And I very much like the way DIFF picks up the "next lower version"
as the default for the second file specification, so I can just do:

$ diff myfile.cob
$ diff myfile.cob.-1
$ diff myfile.cob.-2
$ diff myfile.cob.-3

until I find the change I'm looking for. Very handy...

Just for fun I wrote a short DCL file that checks the number of
days between the ;0 and the ;-0 of each file on our dev system.
Now, I notice from the HELP that F$delta_time only supports a
4-digit return value for the DDDD field, right? It still works,
but it will break in about a year with some files...


dev:[xx.yyy]aaaaaa.OPT;6      12-DEC-2012 12:39:00.94
dev:[xx.yyy]aaaaaa.OPT;2       6-MAR-1986 09:11:42.00

Or a more recently change file:

dev:[xx.yyy]bbbbbb.COB;9       2-NOV-2017 10:08:56.19
dev:[xx.yyy]bbbbbb.COB;7      24-SEP-1991 11:16:27.00

OK, it is not that common that we actually need to look into
one of the files from the 80's or the 90's, but anyway...