Re: Associative array ordering and selective unset (Re: Example function)

["Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxx>]

On Feb 1,  5:39pm, Bruce Stephens wrote:
} Subject: Re: Associative array ordering and selective unset (Re: Example f
}
} It would be a bit tricky to reorder the associative array, wouldn't
} it?  i.e., if I set up some configuration, and then want to insert
} some pattern before some others, then I'd need to recreate the
} associative array.  Maybe that's OK, but it feels a bit awkward.

I just thought of a really clever way to do the specific example that I
gave.  Assume for a moment that the (q) modifier were implemented, i.e.
that (almost repeating the original example) given

        typeset -A map
        map=('*.(gz|Z)' zcat
             '*.bz2' 'bzip2 -dc'
             '*.bz' 'bzip -dc'
             '*' '<')

then ${map[(q)$argv[i]]} returns the value for the first subscript match
found, and ${map[(Q)$argv[i]]} returns the array of values for every key
that matches the subscript.

(Note that I moved the (qQ) into the subscript flags, which is probably
where it really has to be.  And I still hope for a better letter.)

Now change the assignment a little:

        map=('*.(gz|Z)' ': 1; zcat
             '*.bz2' ': 2; bzip2 -dc'
             '*.bz' ': 3; bzip -dc'
             '*' ': 4; <')

Now we can use the (o) substitution flag like so:

	eval ${${(o)map[(Q)$argv[i]]}[1]} '$argv[i]'

That says "find all the values for which the key is a pattern that matches
$argv[i], sort them in ascending order, take the first one, and evaluate
it as a command with argument $argv[i]."  By embedding the "preferred"
ordering in the value as a leading ":" command, we're assured of always
getting the most-specific match.

Now, if only this actually worked ... I'm about to be tied up in a several-
week consulting job, so I probably won't get a chance to do anything with
this anytime soon.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com