From: Robert Klemme <shortcutter@...>
Date: 2010-01-22T17:33:13+09:00
Subject: Re: an elegant way to modify all lines from file by using map() 	function?

2010/1/21 Charles Oliver Nutter <headius@headius.com>:
> On Thu, Jan 21, 2010 at 4:20 PM, RobertGawron <mojwpisdao@gmail.com> wrote:
>> but in your language I didn't find the way to create in one step array
>> of all lines from file, that could be used by map(). If I really want
>> to use map in this situation I have to use secondary array (called
>> arr) like in this snippet?
>>
>> arr = Array.new
>> File.open('foo').each_line{ |l| arr.push l }
>> p arr.collect{ |l| l.upcase }
>
> On 1.8.7+, you can use .lines to get an Enumerator:
>
> p File.open('foo').lines.map {|l| l.upcase}

This does not close the file handle properly.

I'd rather do something like this:

File.foreach('foo').map {|l| l.upcase}

File.foreach('foo').map(&:upcase)

These have the advantage over some of the presented solutions that
they do not create two large Arrays in memory but just one - the
mapped version.

Kind regards

robert

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