More Light! More Light! :: The beauty of Ruby’s array subtraction operator

{ 2008 06 02 }

The beauty of Ruby’s array subtraction operator

Today I had to a set of email addresses, one per line, from which I had to remove the addresses of folks that said “Don’t email me.” Those emails were in a separate file, one address per line.

I figured I’d have to do this again, so I wrote a ruby script to automate it. Below, stripper.rb

#put each address in an array, remove whitespace and make it all lowercase
 potential_emails = IO.readlines(”potentials.txt”).map! {|email| email.strip.downcase}
 delete_emails = IO.readlines(”donotemail.txt”).map! {|email| email.strip.downcase}

#use the beauty of ruby’s array subtraction operator
 puts potential_emails - delete_emails

Simple, terse and readable. Lovely!

{ 2 }

Comments

Nate | 03-Jun-08 at 3:47 pm | Permalink

I gotta admit that’s pretty nice - three lines! It would take me considerably more in Perl…
MattK | 04-Jun-08 at 3:44 pm | Permalink

You can eventually write ANYTHING in one line of Perl.

You could definitely make this one line as well. The arrays potential_emails and delete_emails are there for readability.

it coulda been
puts IO.readLines(”potentials.txt”).map! {|email| email.strip.downcase} - IO.readlines(”donotemail.txt”).map! {|email| email.strip.downcase}

How’s that for terse?

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