From: Daniel Carrera <dcarrera@...>
Date: 2002-11-21T02:30:13+09:00
Subject: Re: Learning Ruby

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

Nope.  The following works:

#!/usr/bin/perl
hello("Daniel");

sub hello {
        $name = $_[0];
        print "Hello $name\n";
}


> Yes, in Ruby [snip] you can do things  like:
>
> if RUBY_PLATFORM =~ /win/
>   require "Win32Defs"
> elsif RUBY_PLATFORM =~ /nix/
>   require "UnixDefs"
> end
>
> OR, [snip]
>   if ENV['FOO'] && ENV['FOO'] == "true"
>     require 'foo'
>     include FooMod
>   elsif ENV['BAR'] && ENV['BAR'] == "true"
>     require 'bar'
>     include BarMod
>   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.

Actually, the same things would work with Perl's "require", but AFAIK not
with "use".


But this points to a difference between Perl and Ruby.  Take the following
Perl code:

sub hello { print "hello" }
hello;
sub hello { print "hi" }
hello;

This will print:

hi
hi

Where as the Ruby version would print

hello
hi

So I can see a bit of a trade-off.  Ruby allows me to redefine functions
at run-time, which can be very cool.  For instance, I can make a
"vector" class, and redefine the method "+" several times to correspond to
different metrics.

Thank you all for the help.  The resources are very good.

Daniel.