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Add description of local kw in global scope #42794

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merged 5 commits into from
Jan 14, 2022
Merged

Add description of local kw in global scope #42794

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ec6f594
Add description of local kw at top-level
tomtuamnuq Oct 25, 2021
57e6e72
Merge branch 'JuliaLang:master' into docpatch-2
tomtuamnuq Jan 11, 2022
d0431fe
Fix doctest
tomtuamnuq Jan 11, 2022
d4c39d8
make explanation clear without scope
tomtuamnuq Jan 12, 2022
5b2a5d9
add global and fix whitespace
tomtuamnuq Jan 12, 2022
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13 changes: 13 additions & 0 deletions doc/src/manual/variables-and-scoping.md
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Expand Up @@ -99,6 +99,19 @@ julia> module E
ERROR: cannot assign variables in other modules
```

Each top-level expression has an invisible scope block around it. If a top-level expression contains a variable declaration with keyword `local`, then that variable is in the local scope of that expression. An example is to declare `local x` in a `begin` or `if` block at the top-level:
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Each top-level expression has an invisible scope block around it.

I think that statement is a bit confusing, since toplevel expressions don't introduce an actual scope block like let or while where new assignments are always scoped by default. We should make clear that this only affects variables with an explicit local declaration.

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This is why I don't feel like I can clearly explain what's happening here. Is there a scope or not? If there isn't a scope, then what is the variable local to? Maybe there's a way to explain it, but if so, I don't know how to.

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I think I would mostly leave out the word scope here and just say that local inside top-level expressions means that the variable won't be accessible outside that expression.

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@simeonschaub Since the usage of scope seems to be confusing here I removed it.


```jldoctest
julia> x = 1
begin
local x = 0
@show x
end
@show x;
x = 0
x = 1
```

Note that the interactive prompt (aka REPL) is in the global scope of the module `Main`.

## Local Scope
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