From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-03-25T17:35:03+09:00
Subject: Re: hash problem

On Thu, Mar 25, 2010 at 9:16 AM, Adam Nelreth <nelreth@gmail.com> wrote:
> Hi
>
> I have small problem with adding data to hash table
>
> In loop I take some string and get IP address from it like this:
>
> ip =
> /(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/.match(title)
>
> and now under ip variable I have my IP which I want to put in hash table
> and count if the same IP I will find in another step (loop)
>
> I create hash table
> test = Hash.new
> and put it in table
> test[ip] = 1
>
> But I don't know how to search table to find if the same ip is already
> in table and increase counter
>
> Could You tell me how to do this or give me just a clue how to figure
> this out ?

A typical idiom is this:

irb(main):007:0> h = Hash.new(0)
=> {}
irb(main):008:0> h["10.1.1.1"] += 1
=> 1
irb(main):009:0> h["10.1.1.1"] += 1
=> 2
irb(main):010:0> h["10.1.1.2"] += 1
=> 1
irb(main):011:0> h["10.1.1.3"] += 1
=> 1
irb(main):012:0> h
=> {"10.1.1.1"=>2, "10.1.1.2"=>1, "10.1.1.3"=>1}

That constructor of Hash receives a default value for a non-existing
key, so when you do this:

h[k] += v

it means

h[k] = h[k] + v

The right hand side h[k] evaluates to the default value if k is not in
the hash, as in your case the first time you add an IP.

Jesus.