This global vs local scoping really has me confused. I understood that for loops have their own scope, so I was expecting this to error out, but it doesn’t. julia> temp = 10 10 julia> for i in 1:5 println(temp) end 10 10 10 10 10 Since I didn’t declare the variable temp inside …

Here temp is a global variable and in Julia you can read from global variables anywhere (in the same module - here Main) just not assign to them. If you want to assign to a global variable then you need to declare it with a global statement.

From Scope of Variables · The Julia Language "In a local scope, all variables are inherited from its parent global scope block unless: * an assignment would result in a modified global variable, or * a variable is specifically marked with the keyword local . Thus global variables are only inheri…

OK, I think I see. what is outside the for loop is defaulted to global, but what is defined within the for loop is local so after the loop completes, I cannot get those variables out, but I can get upstream global variables into the for loop to use. I know there is another whole topic on this, but…

[image] jonjilla: I know there is another whole topic on this, but this is really unintuitive for people coming from other scripting languages. I agree. But it is really complicated. Difficult to decide for which use case to optimize.

Yes, a number of people think similarly and so I think it’s likely to change in the (near-ish?) future if I read the other thread correctly.

Not wanting to add more noise to this topic, but just how I think about this. A function is like a black box so variables go in (through the function arguments) and variables go out through return statements, so that’s makes sense that functions that their own scope. But for, try, while blocks don…

[image] jonjilla: creating a black box with only a clear mechanism to get things in but not out. I don’t understand this statement. If you write global temp = 20 within the for-loop then there is a very clear mechanism to get things out, isn’t it?

I mentioned, “other than setting variables as global” in my statement. But that feels like a workaround and seems kind of heavy handed. It feels like there should be another way other than resorting to globals. Anyways, I don’t think I’m going to add anything useful to this discussion. I don’t…

…I’m also ‘just a simple user’ :wink:

I also find the new policy about global scopes and for loops quite complicated and confusing. Sure it can be justified (everything can, in the end), but would really like to change it back to what it was before the big changes of 0.7.0 (my two cents). Still somebody here pointed out that there is a…

Confused about global vs local scoping in for loops in 1.0

New to Julia

Tamas_Papp October 15, 2018, 7:50am 12

is one of the latest ones.

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Confused about global vs local scoping in for loops in 1.0

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