Re: Looping through file for regex

From: James Edward Gray II (james_at_grayproductions.net)
Date: 01/02/04 

Date: Fri, 2 Jan 2004 11:09:37 -0600
To: "Ed Christian" <edc@corp.ptd.net>

On Jan 2, 2004, at 10:46 AM, Ed Christian wrote:

> James Edward Gray II wrote:
>> On Jan 2, 2004, at 10:10 AM, Paul Kraus wrote:
>>
>>>> Don't do that. The foreach reads the whole file into memory and
>>>> then walks it line by line. If we just want one at a time, let's
>>>> fetch them that way
>>>
>>> I don't agree with this.
>>
>> And I don't understand this. ;)
>>
>>> If you are working with a file that is as small as
>>> the one included seems to be easier to just load up some data
>>> structures. I understand writing efficient code is always best but
>>> for a quickie script like this I wouldn't be to concerned with the
>>> 1/100th of a ms that your going to shave off but not dumping the
>>> contents to memory.
>>
>> If you're going to work with the lines one at a time anyway, what
>> exactly is the advantage of using the probably slower and definitely
>> more memory wasteful foreach()?
>
> While the foreach is certainly more wasteful, why in the world would
> you
> re-initialize and re-open the file multiple times? Why not just open
> the
> file once and iterate over the file, comparing each line of the file to
> each of the keys in the %input hash?

Your way is certainly better, if output order doesn't matter. The
original code checked the first key against the file, then second, then
third. Your suggestion could find the sixth index before it finds the
first. If the order doesn't matter though, I agree that your
suggestion would be boatloads more efficient.

James

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