Date: 03 Jul 2001 10:48:08 -0500
From: Ren Maddox <ren@tivoli.com>
Subject: Re: map/hash question, functional style
Message-Id: <m37kxqnhdz.fsf@dhcp9-173.support.tivoli.com>

On 3 Jul 2001, mordor@fly.srk.fer.hr wrote:

> I have a list of hash keys in a variable like this:
> @keys = qw(key1 key2 key3);
> 
> and a list of values:
> @vals = (1, 2, 3);
> 
> Now, what is the most elegant way to make a hash from this? I'd
> prefer using map and not foreach if at all possible. This is my
> current code:

@hash{@keys} = @vals;

> $i = 0;
> %hash = map { $keys[$i++] => $_ } @vals;
> 
> Is there a way to avoid global counter?

Well, if you really wanted to loop, you *could* loop over the indices:

$hash{$keys[$_]} = $vals[$_] for 0..$#keys;

(You could use map the same way, but there's really no point.)

> Also, except map and grep, what other functional programming
> constructs are present in perl? Can map and grep be generalized to
> iterate over more than one array?

Both map and grep work on lists, not arrays.  In list context, an
array produces a list of its elements.  There is no reason that
multiple arrays cannot be used in that way:

map { $_ *= 2 }, @ary1, @ary2, @ary3;

-- 
Ren Maddox
ren@tivoli.com