Re: ${(kv)foo[bar]}

[Bart Schaefer <schaefer@brasslantern.com>]

On Apr 3, 10:00pm, Andrey Borzenkov wrote:
} Subject: Re: ${(kv)foo[bar]}
}
} Although it is rather hard to understand why ${(kv)opt_args[(i)--media]} 
} should work and ${(kv)opt_args[--media]} not.

The rationalization is that with [(i)...] the subscript is a pattern, so
you may not know in advance what it's going to match, and therefore it
is useful to be able to return both the key and the value.  [(i)--media]
is a degenerate case where the pattern is a plain string.  Without the
(i), the subscript is always a plain string and therefore known, and you
don't need to be able to expand it.

The real reason, as I said, is that the implementation of subscripting
with [(i)...] does a scan of the hash keys rather than a simple hash
lookup; it's got code that's shared with (R) and (I) and therefore is
designed to return an array.  Implementing subscripting with a full
scan in the ordinary case just for (kv) would foil the reason for using
a hash table to begin with.