Re^4: Hash assignments using map

Thanks varian. This makes sense.

I want to quickly create a hash with keys that are the elements of the list. All I want access to is the keys...I don't care what the values are. I can then use exists to see if those keys either do or do not exist in another hash.

Thanks again!

Comment on Re^4: Hash assignments using map Download Code

Replies are listed 'Best First'.
Re^5: Hash assignments using map by shmem (Chancellor) on Feb 24, 2007 at 20:32 UTC
All I want access to is the keys... ok, but a hash has a key and a value. So your code should be: `my @keys = qw{ a b c d }; my %hash = map { $_,1 } @keys;` [download] if you want your keys unaltered. If you want a "string increment" (`$_="a";$_++; # $_ is b now`) its ok to use `$_++`. In the loop `my %hash; foreach ( @keys ) { $hash{$_}++; }` [download] you are also using two variables - in a shortcut: you create a new hash slot with key `$_` you increment (the previously undefined) value for that key So, it's the same thing with keys and values here. With map iterating over an array of keys, you must provide a value to have pairs to be stored as (key,value) in a hash. --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^5: Hash assignments using map
by shmem (Chancellor) on Feb 24, 2007 at 20:32 UTC

All I want access to is the keys...

and

my @keys = qw{ a b c d };
my %hash = map { $_,1 } @keys;
[download]

$_="a";$_++; # $_ is b now

$_++

In the loop

my %hash;
foreach ( @keys ) {
    $hash{$_}++;
}
[download]

you are also using two variables - in a shortcut:

you create a new hash slot with key $_
you increment (the previously undefined) value for that key

So, it's the same thing with keys and values here. With map iterating over an array of keys, you must provide a value to have pairs to be stored as (key,value) in a hash.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

[reply]
[d/l]
[select]