Re: Learning Ruby

In article <[e-mail]>,
Daniel Carrera  <[e-mail]> wrote:
>Hi,
>
>I am a Perl hacker trying to get to know Ruby.  I have two questions:

Welcome... I used to do Perl a few years back, then I found Ruby ;-)

>
>1)  What is a good resource for learning Ruby in general?  Is there a Ruby
>equivalent to "Learning Perl"?

Well, since you know Perl I'd recommend the 'pickaxe' book: "Programming 
Ruby: The Pragmatic Programmer's Guide" by Dave Thomas and Andrew Hunt.
Also available online at:
http://165.193.123.250/book/index.html
(there's currently a problem with the registration of the rubycentral 
domain, hence the use of numbers in the URL)

The pickaxe is a great book for learning Ruby (if you're familiar with 
programming in general already) and it is also has a very good library 
reference section.

>
>2)  Where does Ruby lie in the interpreted vs compiled range?
>For instance, Perl is not really interpreted.  The file is compiled into
>an object code which is then run.  This causes a speed benefit, and allows
>for some flexibility.  Is Ruby like that?  or it is JIT-compiled? or is it
>truly interpreted, like the shell?

Ruby is interpreted - The parser creates an AST that is walked.  There are 
projects in the works to create a RubyVM (Rite, or Ruby 2.0) as well as 
Cardinal (Ruby frontend for the ParrotVM).  Being interpretted does effect 
the speed of execution to some extent, but Ruby actually does pretty well 
in the language shootout rankings.  Generally not as fast as Perl, but not 
too much slower.


>I noticed that Ruby doesn't let me use functions until after I define
>them (unlike Perl).  Why is that?  I want to have the freedom to define
>the functions anywhere.
 
But even with Perl, don't you have to pre-declare the function prototype?

Yes, in Ruby you do need to have the function predeclared prior to using 
it.  That's because there's really no distinction between compile-time and 
runtime in Ruby.  This actually is a very nice feature: you can do things 
like:

if RUBY_PLATFORM =~ /win/
  require "Win32Defs"
elsif RUBY_PLATFORM =~ /nix/
  require "UnixDefs"
end

OR, things like conditional inheritance or conditional mixins based on 
some environment setting, for example:

#conditional mixin
class Foo
  if ENV['FOO'] && ENV['FOO'] == "true"
    require 'foo'
    include FooMod
  elsif ENV['BAR'] && ENV['BAR'] == "true"
    require 'bar'
    include BarMod
  end
 
  #rest of class definition...

end

It's probably not as easy to do that sort of thing in Perl because there 
is a seperate compile phase.  But, I have to admit, it's been a while so I 
wouldn't be surprised if there is a way of doing this in Perl.

Phil