Good notes posted by svoop

Map-like Manipulation of Hash Values

Let’s say you want to multiply all values of the following hash by 2:

hash = { :a => 1, :b => 2, :c => 3 }

You can’t use map to do so:

hash.map {|k, v| v*2 }   # => [6, 2, 4]

However, with merge you can:

hash.merge(hash) {|k,v| v*2 }   => {:c=>6, :a=>2, :b=>4}

(The above is Ruby 1.8, in Ruby 1.9 the order is preserved.)

Cheat Sheet

I have written a short introduction and a colorful cheat sheet for Perl Compatible Regular Expressions (PCRE) as used by Ruby’s Regexp class:

http://www.bitcetera.com/en/techblog/2008/04/01/regex-in-a-nutshell/