From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2001-05-11T04:10:09+09:00
Subject: [ruby-talk:14957] load and local variable scope (and constants too)


if I have  a file that contains:
#####start of x.rb #####
suffix = "v"
####end of x.rb ######

and another file loads that file and tries to use the variable suffix:
#######start of y.rb #####
load "x.rb"
puts "suffix is: #{suffix}"
######end of y.rb #####

and then run y.rb, the output is:
y.rb:2: undefined local variable or method `suffix' for 
#<Object:0x40184c90> (NameError)

So that tells me that local variables have file scope and that doesn't 
change when the file defining the local is loaded (ie. I can't access a 
local variable defined in another file even if that file is loaded).  
Makes sense.

But, if I have:

#####start of x.rb #####
SUFFIX = "v"
####end of x.rb ######

and y.rb has:
#######start of y.rb #####
load "x.rb"
puts "suffix is: #{SUFFIX}"
######end of y.rb #####      

and then run y.rb, I get:
suffix is: v 

So it seems like locally defined constants have a different scope than 
locally defined variables - constants can transcend the file scoping if 
the file they are defined in is load'ed or require'd.

In the next case I declare suffix as global with '$':
##### start of x.rb ######
$suffix = "v"
##### end of x.rb #####

#### start of y.rb #####
load "x.rb"
puts "suffix is: #{$suffix}"
#### end of y.rb   #####

and when y.rb is run, as expected it works (because $suffix is global)

So, am I right in concluding that in regard to file scoping, constants 
look more like globals?  I suppose this makes sense since if you try to 
redefine a constant you'll get a warning which will indicate that perhaps 
you have another constant by the same name in a differnt file.

Phil