[Cuis] A small variation to use provides / requires

[Ken Dickey]

> .. when I've a package that have several req and at the same time this
package is a req of more than 1 different package, that at the same time
might have different req between them and coexist in the same image,...

My recollection of a discussion with Dave Simmons about Smalltalk Agents is that one can associate revision information with selector lookup/dispatch to allow for multiple, different versions of software to run in the same image.  I believe this was done in SmalltalkAgents.

This is very useful when developing so that the debug tools can use the old, stable version when debugging new development tools.  [This is also done in some Scheme systems].

The current provide/requires allows for this by supplying the version & revision information.

It is true that we currently do not make use of this in package checking, but the code would be easy to add.

The guide is that we try to do useful things in the most simple way we can and then make things more smarter and more complex when and if we need to.


Having a package specify its direct requirements helps here.

If one separates the requirement description from the package, then the package and its description can get out of synchronization -- the wrong version information could be used.  

One more thing I have to track and update.  One more thing to go wrong.

This is less of a danger when the description is part of the package.

IMHO, package management is easier.  When I change a package, the revision number is incremented so when the package is saved I know it is a new revision.

If two packages have conflicting requirements, each package requiring other packages with  incompatible versions, then the code can check and deal with that.

Incompatible requirements are like missing requirements -- it means that you can't safely use the mix of code packages together.  

It is much better to know this before the code is loaded, no?


It would help me if
  Feature require: 'Swazoo'

Actually loaded Swazoo...

$0.02
-- 
Ken [dot] Dickey [at] whidbey [dot] com