# Side discussion on gotos

**URL:** <https://discourse.julialang.org/t/side-discussion-on-gotos/16821>\
**Category:** Internals & Design\
**Created:** [October 26, 2018, 10:50am UTC](https://discourse.julialang.org/t/side-discussion-on-gotos/16821 "2018-10-26T10:50:30Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![foobar\_lv2](https://avatars.discourse-cdn.com/v4/letter/f/ee59a6/32.png) [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)\
**Post date:** [October 26, 2018, 12:10pm UTC](https://discourse.julialang.org/t/side-discussion-on-gotos/16821/3 "2018-10-26T12:10:44Z")

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Afaik, goto is a primitive. It is simply a decision of surface syntax that you use it as a macro instead of keyword. If you look at `code_typed(...; optimize=false)` and `code_lowered` you will see it all over the place. As far as I understood, Stefan’s solution disregards the abstract syntax tree (the thing manipulated by macros, with expressions) and instead considers lowered code and the resulting control flow graph. Lowered code does not contain loops:

```julia
julia> function f(A)
       x=A[1]
       @goto skip
       return y
       @label skip
       while x>0
       x-=1
       end
       x
       end;

julia> code_lowered(f, Tuple{Vector{Int}})
1-element Array{Core.CodeInfo,1}:
 CodeInfo(
2 1 ─ x = (Base.getindex)(A, 1) │
3 └── goto #3 │
4 2 ─ return Main.y │
6 3 ┄ %4 = x > 0 │
  └── goto #5 if not %4 │
7 4 ─ x = x - 1 │
  └── goto #3 │
9 5 ─ return x

```

In this sense, loops are not primitive structures in julia. Stefan’s rule needs to operate on a level between AST and lowered code: We see that currently, the lowering already decides whether bindings are local or global. With his rule, we would need to “semi-lower” without this knowledge, then search the CFG, then annotate local/global, and then go on as before. People who want to _really_ understand scoping in top-level would need to understand the lowering process as well as parsing (AST construction).

PS. Thanks @StefanKarpinski for moving us out of the main thread!

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