From: Mark Wilson <mwilson13@...>
Date: 2002-11-20T12:58:48+09:00
Subject: Re: Learning Ruby

I am also new to Ruby (and to programming in general).  I have found 
the book "Teach Yourself Ruby in 21 Days" , by Mark Slagell, to be very 
helpful (it was my second book after "Programming Ruby".  There is also 
a Ruby User's Guide online at http://www.ruby-lang.org/~slagell/ruby/.

On Tuesday, November 19, 2002, at 10:51 PM, Phil Tomson wrote:

> In article 
> <Pine.GSO.4.44.0211191855480.3450-100000@hardy.math.umd.edu>,
> Daniel Carrera  <dcarrera@math.umd.edu> 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
>
>