# Further Clarification on scoping rules

**URL:** <https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373>\
**Category:** New to Julia\
**Tags:** question, arrow\
**Created:** [March 21, 2023, 6:58am UTC](https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373 "2023-03-21T06:58:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![phantom](https://avatars.discourse-cdn.com/v4/letter/p/e0b2c6/32.png) [@phantom](https://discourse.julialang.org/u/phantom)\
**Post date:** [March 21, 2023, 6:58am UTC](https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373/1 "2023-03-21T06:58:59Z")

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Sorry if I am overlooking something again. But according to the documentation on [Scope](https://docs.julialang.org/en/v1/manual/variables-and-scoping/):

`Variables in outer scopes are visible from any scope they contain — meaning that they can be read and written in inner scopes — unless there is a local variable with the same name that "shadows" the outer variable of the same name.`

`When we say that a variable "exists" in a given scope, this means that a variable by that name exists in any of the scopes that the current scope is nested inside of, including the current one. `

So I am confused why something like this returns an error

```julia
function dinner(A)
    eat()
end

function eat()
    println("eat $A")
end

dinner("Apple")
ERROR: UndefVarError: A not defined

```

Why isn’t the variable `A` as defined by `dinner` visible inside the function `eat`? It seems as though it would be given that `eat` is in the inner scope of `dinner`?

Moreover as functions introduce a hard scope where:

`If x is not already a local variable and assignment occurs inside of any hard scope construct (i.e. within a let block, function or macro body, comprehension, or generator), a new local named x is created in the scope of the assignment;`

```julia
A = "pear"
"pear"

dinner("apple")
eat pear 

```

I am uncertain why `eat` is overlooking the local variable `A` it is nested in, but accepting the global variable `A`. Would someone be able to clarify this point? My untutored reading of the documentation seems to indicate that the opposite would be true.

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<div class="post-metadata">

**Author:** ![Salmon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/salmon/32/22968_2.png) [@Salmon](https://discourse.julialang.org/u/Salmon)\
**Post date:** [March 21, 2023, 7:06am UTC](https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373/2 "2023-03-21T07:06:40Z")

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The scope of something depends on where that object is _defined_ rather than where it is called. The function `eat` is defined in global scope, therefore it does not see the local variables of other functions (but it does see global variables).

If it were the other way around, chaos would ensue.

Another way to see the difference is to define a closure instead, which is a function defined in the local scope of another function:

```julia
function dinner(A)
  function eat()
    println("eat $A")
  end
  eat()
end

```

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**Author:** ![torrance](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/torrance/32/38990_2.png) [@torrance](https://discourse.julialang.org/u/torrance)\
**Post date:** [March 21, 2023, 7:20am UTC](https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373/3 "2023-03-21T07:20:32Z")

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This is the difference between lexical scoping and dynamic scoping. There’s an interesting history of the two scoping rules you can read up on, aiui dynamic scoping was the earlier of the two.

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<div class="post-metadata">

**Author:** ![phantom](https://avatars.discourse-cdn.com/v4/letter/p/e0b2c6/32.png) [@phantom](https://discourse.julialang.org/u/phantom)\
**Post date:** [March 21, 2023, 7:21am UTC](https://discourse.julialang.org/t/further-clarification-on-scoping-rules/96373/4 "2023-03-21T07:21:37Z")

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oh wow…that clears up a lot of the confusion I’ve been having. Thanks so much guys!