From: Peter <Peter.Vanbroekhoven@...>
Date: 2003-09-20T07:48:10+09:00
Subject: Re: Defining constants in global scope

> My guess is, and I'm new to Ruby so I'm probably wrong, that you first 
> need to open the "global" Module or class for which you want to define 
> the constant for. In this case this would be the Kernel module.

Look at the transscript below. Apparently toplevel constants don't really
belong to the Kernel module. However if a constant is defined at the
toplevel, and doesn't clash with a constant in the Kernel module, you can
access it in the Kernel module, but you get a warning. Also toplevel
constants can be read as ::MyConstant, but not assigned. Somehow this
behavior seems a bit inconsistent to me. Also I would never allow access
to toplevel constants through the Kernel module because if you use someone
else's code which defines a constant with the same name in the Kernel
module (should someone ever want to do such a thing), you're in for one
big bug hunting safari. But that's why it gives a warning I guess, but
it's human nature to ignore warnings, especially when the code still
works...

Peter

irb(main):001:0> MyConstant = 1
=> 1
irb(main):002:0> MyConstant
=> 1
irb(main):003:0> ::MyConstant
=> 1
irb(main):004:0> Kernel::MyConstant
(irb):4: warning: toplevel constant MyConstant referenced by
Kernel::MyConstant
=> 1
irb(main):005:0> Kernel::MyConstant = 2
=> 2
irb(main):006:0> MyConstant
=> 1
irb(main):007:0> ::MyConstant = 2
SyntaxError: compile error
(irb):7: syntax error
::MyConstant = 2
              ^
        from (irb):7
irb(main):008:0> Kernel::MyConstant
=> 2