From: Jason Foreman <threeve.org@...>
Date: 2005-07-08T05:00:46+09:00
Subject: Re: Inconsistent(?) when including modules

On 7/7/05, Paulo Jabardo <pjabardo@yahoo.com.br> wrote:
> I was playing around with modules when I noticed that
> I counld, for example include Math and use sin,cos,etc
> as if it were a common method. When I tried to do the
> same in irb
> 
> module Test
>   def Test.triple(x)
>      3*x
>   end
> end
> 
> Test.triple 2 => 6
> 
> If I include Test from the toplevel
> inlcude Test
> 
> and then call triple directly I get an error:
> irb(main):005:0> triple 2
> NoMethodError: undefined method `triple' for
> main:Object
>         from (irb):5
> 
> 
> I then tried to implement the same module as an
> extension:
> 
> #include <ruby.h>
> 
> static VALUE triple(VALUE self, VALUE x){
>   return rb_float_new(3.0*NUM2DBL(x));
> }
> 
> VALUE modulo;
> 
> void Init_TestC(){
>   modulo = rb_define_module("TestC");
>   rb_define_module_function(modulo, "triple", triple,
> 1);
> }
> 
> When I load this extension,
> require 'TestC.so'
> 
> TestC.triple 2 => 6
> 
> include TestC
> triple 2 => 6   # No error
> 
> I haven't seen this documented. Can I get this same
> behaviour from ruby code or do I need to write an
> extension?
> 


You ruby module and extension module are not equivalent.  Try instead this:

module Test
  def triple(x)
    3*x
  end
  module_function :triple
end

Test.triple 2  # => 6

include Test
triple 2       # => 6



Jason



> Thanks
> 
> Paulo Jabardo
> 
> 
> 
> 
> 
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