Style/Structuring question: One vs. multiple global objects

[Kirk McDonald]

Henning Hasemann wrote:
> I think the paranoia about globals comes from some experiences with or
> hints for other programming languages such as python etc... where
> globals are generally considered bad style, though I must confess I
> never understood why there is/was such a radical talking against them.
> 

Globals are much less annoying in D than in Python. They are annoying in 
Python because of Python's scoping rules. For the benefit of those who 
don't know Python, the issue is this:

i = 12
def foo():
     print i # prints '12'
     i = 20
foo()   # call foo
print i # prints 12; foo did not change 'i'

When it assigns 20 to 'i' inside of foo(), it is actually creating a new 
name local to foo(), which shadows the global name. To assign to the 
global name instead, you must use the 'global' keyword.

j = 14
def bar():
     global j
     print j # prints '14'
     j = 40
bar()
print j # prints '40'; bar changed 'j'

You might expect this to lead to some confusion (particularly among 
newbies to Python), and you'd be right. It is because of this 
potentially confusing situation that globals are generally frowned upon 
in Python.

In D, on the other hand, variables have to be explicitly declared. If 
the only variable with a certain name is at global scope, then using 
that name will obviously only refer to the global variable:

int i;
void foo() {
     i = 12; // changes the global
}

D goes further by making the shadowing of global variables an error, and 
making ambiguous situations in general errors. I am much less hesitant 
to use globals in D than I am in Python.

-- 
Kirk McDonald
http://kirkmcdonald.blogspot.com
Pyd: Connecting D and Python
http://pyd.dsource.org