# How to use the macro @label and @goto

**URL:** <https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247>\
**Category:** General Usage\
**Created:** [June 4, 2022, 7:38pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247 "2022-06-04T19:38:40Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![Raymond](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raymond/32/36557_2.png) [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Post date:** [June 4, 2022, 7:38pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/1 "2022-06-04T19:38:40Z")

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Dear all,

I want to know how to use @label and @goto. Can you give me an example to use them?  
Many thanks.

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**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [June 4, 2022, 8:39pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/2 "2022-06-04T20:39:47Z")

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The Julia docs probably should have an example.

The function below is horrendous, it is defined only for the purpose of this example, it could be rewritten to be much better but then it would not serve the purpose of illustrating `@goto`/`@label`.

The only motive I think it is reasonable to use `@goto` is to break out of multiple loops at once. Other languages allow the keyword `break` to be accompanied by a number indicating how many nested loops the `break` is affecting (from the inner to outer). Julia does not have this feature so, for this specific use case, `@goto` is more elegant than adding a lot of flags and `if`s to achieve the same effect.

```julia
julia> function has_zero(A)
           i, j = 0, 0
           for outer i in 1:size(A, 1)
               for outer j in 1:size(A, 2)
                   if iszero(A[i, j])
                       @goto after_loop
                   end
               end
           end
           @label after_loop
           if iszero(A[i, j])
               return i, j
           end
           return false
       end
has_zero (generic function with 1 method)

julia> A = [1 2 3; 4 5 6]
2×3 Array{Int64,2}:
 1 2 3
 4 5 6

julia> has_zero(A)
false

julia> A = [1 2 3; 0 5 6]
2×3 Array{Int64,2}:
 1 2 3
 0 5 6

julia> has_zero(A)
(2, 1)

```

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<div class="post-metadata">

**Author:** ![Raymond](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raymond/32/36557_2.png) [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Post date:** [June 4, 2022, 9:20pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/3 "2022-06-04T21:20:13Z")

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> [@Henrique\_Becker](#):
>
> ```julia
> function has_zero(A)
> i, j = 0, 0
> for outer i in 1:size(A, 1)
> for outer j in 1:size(A, 2)
> if iszero(A[i, j])
> @goto after_loop
> end
> end
> end
> @label after_loop
> if iszero(A[i, j])
> return i, j
> end
> return false
> end
> 
> ```

What is the advantage of `@goto` and `@label`? In your example, Why not directly write the codes as below?

```julia
function has_zero(A)
                  i, j = 0, 0
                  for outer i in 1:size(A, 1)
                      for outer j in 1:size(A, 2)
                          if iszero(A[i, j])
                              return i, j
                          end
                      end
                  end
                  return false
              end

```

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**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [June 4, 2022, 9:27pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/4 "2022-06-04T21:27:26Z")

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```julia
julia> using Multibreak

julia> @multibreak function has_zero(A)
           i, j = 0, 0
           for outer i in 1:size(A, 1)
               for outer j in 1:size(A, 2)
                   if iszero(A[i, j])
                       break; break
                   end
               end
           end
           if iszero(A[i, j])
               return i, j
           end
           return false
       end
has_zero (generic function with 1 method)

```

The `@multibreak` macro rewrites the double `break` to exactly the same `@goto` and `@label` construction, of course.

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**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [June 4, 2022, 9:29pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/5 "2022-06-04T21:29:35Z")

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> [@Raymond](#):
>
> What is the advantage of `@goto` and `@label`? In your example, Why not directly write the codes as below?

You have the answer above:

> [@Henrique\_Becker](#):
>
> The function below is horrendous, it is defined only for the purpose of this example, it could be rewritten to be much better but then it would not serve the purpose of illustrating `@goto`/`@label`.

---

<div class="post-metadata">

**Author:** ![Raymond](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raymond/32/36557_2.png) [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Post date:** [June 4, 2022, 9:32pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/6 "2022-06-04T21:32:03Z")

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@Henrique_Becker @GunnarFarneback Thanks for both of your help.

---

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**Author:** ![Benny](https://avatars.discourse-cdn.com/v4/letter/b/49beb7/32.png) [@Benny](https://discourse.julialang.org/u/Benny)\
**Post date:** [June 4, 2022, 11:19pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/7 "2022-06-04T23:19:52Z")

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GOTO was routinely written in older programming languages, but it was mostly abandoned decades ago in favor of structured programming, like for-loops, methods, try-catch-finally. The structures are effectively ways to write the more maintainable GOTO patterns, so GOTO stills show up in the lowered and compiled code that the compiler makes from the structures.

Julia’s `@goto` and `@label` has such niche uses that the only application people can immediately think of is multi-level breaks from nested loops, yet it’s been demonstrated in this thread that specific purpose could be written with improved syntax enabled by `@multibreak`. Unlike historical GOTO, Julia’s `@goto`’s ability to jump around the code is limited somewhat, but it can still easily make a program much harder to follow than typical structures. Treat it as a relic of the past, a last resort to dust off if you run into a surprising case where the typical structures would be harder to follow than the equivalent `@goto` version.

---

<div class="post-metadata">

**Author:** ![Raymond](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raymond/32/36557_2.png) [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Post date:** [June 4, 2022, 11:20pm UTC](https://discourse.julialang.org/t/how-to-use-the-macro-label-and-goto/82247/8 "2022-06-04T23:20:43Z")

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Thanks so much.