Why people dislike global variables so much while I find them so convenient?

bachmeier no at spam.net
Tue Jan 25 14:44:01 UTC 2022

On Tuesday, 25 January 2022 at 09:53:25 UTC, rempas wrote:
> It is known that people dislike global variables and the reason 
> is that they make the code harder to debug.

I object to your question. There's not necessarily anything wrong 
with global variables, for loops, goto statements, and whatever 
else some claim you shouldn't use. Maybe you're thinking of 

I don't think it's common that you need global variables in D. If 
you want to share a variable among several functions, use a 
struct. But if a global is the best solution, use the global.

If you've ever had the joy of working with FORTRAN 77 or earlier 
versions of FORTRAN (back when it was in all caps) you understand 
why working with globals can be a traumatic experience. For 
instance, multiple functions in multiple files will sometimes 
change the same global variable.

You have global variable x. foo calls bar which calls baz which 
changes x. Then 75 lines later foo calls goo, which also changes 
x. Even if there's no bug in your code, this style of programming 
will burn threw all your brain energy in a hurry. You have to 
think about the entire program in order to reason about one part. 
It was often easier to rewrite the whole thing from scratch than 
to make a meaningful change involving global variables.

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