On 2009-07-20, at 21:10 , Robert Goldman wrote:
james anderson wrote:
On 2009-05-18, at 14:55 , Nikodemus Siivola wrote:
2009/5/18 Robert Goldman rpgoldman@sift.info:
Tobias C. Rittweiler wrote:
I've read several times that it's a head ache to configure optional dependencies with ASDF.
How true is that? Could we perhaps provide another clause :OPTIONALLY-DEPEND-ON in DEFSYSTEM which would load a system only if available?
Doesn't :WEAKLY-DEPENDS-ON do what you want?
there is at least one more kind of dependency between two components: "contingency".
...
Did this discussion ever go anywhere?
James, would it be possible for you to resend this email with the tables given as a text attachment, rather than as inline text? I don't know about the rest of the list, but my client (Thunderbird) turned your tables into complete and utter gibberish.
[i suspect it was because i neglected to disable line-wrapping before i sent the message.]
to summarize:
in addition to simple and weak dependency, there is at least one more kind of dependency between two components: "contingency".
in order to manage a system for multiple runtimes, each of which entails it's own foreign libraries, i have found it useful to add a constraint called "contingent-on". this may-or-may-not be what you intend with "optionally-depend-on". i have found it useful to express the constraints:
"if a feature|system 'X' is present, then system|component 'Y' is required, and depends on 'X'. if 'X' is not present, do nothing."
i attach an html file which describes, as a table, the relation between system model state and operations.