From: Robert Klemme <bob.news@...>
Date: 2006-02-03T19:18:29+09:00
Subject: Re: Seeking the Ruby way

William James wrote:
> Todd Breiholz wrote:
>> I'm just getting my feet wet with Ruby and would like some advice on
>> how you "old-timers" would write the following script using Ruby
>> idioms. 
>> 
>> The intent of the script is to parse a CSV file that contains 2
>> fields per row, sorted on the second field. There may be multiple
>> rows for field 2. I want to get a list of all of the unique values
>> of field2 that has more than 1 value for the 1st 6 characters of
>> field 1. 
> 
> ---  input data  -----
> 123456ab,900
> 123456cd,900
> 123456ef,909
> 012345gh,909
> ---  end of input  -----
> 
> ---  Using a hash of arrays:
> 
> require 'csv'
> 
> h = Hash.new{ [] }

I wonder how this works since the Hash never stores these arrays.

> CSV::Reader.parse(File.open( ARGV.first )) { |row|
>   h[row.last] |= [ row.first[0,6] ] }
> p h.delete_if{|k,v| v.size == 1 }
> 
> ---  output  -----
> {"909"=>["123456", "012345"]}
> ---  end of output  -----

Is this really the output of the script above?

    robert