From: Robert Klemme <shortcutter@...>
Date: 2008-05-14T20:06:57+09:00
Subject: Re: array diff

2008/5/13 James Dechiaro <jdechiaro@coherecomm.com>:
> if SumArray.include?(row[1])did the trick...thanks adam!
>
>
> Adam Shelly wrote:
>> On 5/12/08, James Dechiaro <jdechiaro@coherecomm.com> wrote:
>>> the problem i'm running into is when i try to open back the csv1 and
>>> compare the SumArray against it in order to get the entire line (not
>>> just the element). It instead prints all the lines, even the ones not
>>> contained in the array.
>>>
>>> So it looks as though the .eql? module is not working correctly.
>>>
>> There are a few potential problems with this line:
>>      records.collect do |row| row[1].eql?(SumArray)
>>
>> First, I think you need an 'if'.  Otherwise you are calling eql? but
>> not using the result.  Second, it looks like you are comparing a
>> single field with the
>> whole SumArray.  They will never be equal.  You probably want something
>> like
>>     if SumArray.include?(row[1])

You might also want to consider using Set or Hash for more efficient
lookups.  The way I would probably do it is this: define a record type
that covers all the relevant information (easily done with Struct).
Then read the file to test against (csv2 I believe) and convert
records to the record type which you then add to the Set / Hash.  Then
read the second file line by line, convert it and print it if it is
not contained in the Set / Hash.  That way you do not need to keep
both files in memory and the Set / Hash lookups are much faster than
Array based lookups.

Kind regards

robert


-- 
use.inject do |as, often| as.you_can - without end