# Can I concatenate expressions in macro?

**URL:** <https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220>\
**Category:** General Usage\
**Created:** [October 5, 2021, 7:48am UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220 "2021-10-05T07:48:33Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Jakub\_Mitura](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jakub_mitura/32/19496_2.png) [@Jakub\_Mitura](https://discourse.julialang.org/u/Jakub_Mitura)\
**Post date:** [October 5, 2021, 7:48am UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/1 "2021-10-05T07:48:33Z")

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i have array of expressions generated in macro and i want to return it all so they will be executed one by one

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**Author:** ![albheim](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albheim/32/34660_2.png) [@albheim](https://discourse.julialang.org/u/albheim)\
**Post date:** [October 5, 2021, 9:13am UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/2 "2021-10-05T09:13:42Z")

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You could look at how a block of expressions is normally represented and try to rebuild that. For example

```julia
julia> a = quote
       a = 1+1
       b = a + 4
       end
quote
    #= REPL[16]:2 =#
    a = 1 + 1
    #= REPL[16]:3 =#
    b = a + 4
end

julia> dump(a)
Expr
  head: Symbol block
  args: Array{Any}((6,))
    1: LineNumberNode
      line: Int64 2
      file: Symbol REPL[16]
    2: Expr
      head: Symbol =
      args: Array{Any}((2,))
        1: Symbol a
        2: Expr
          head: Symbol call
          args: Array{Any}((3,))
            1: Symbol +
            2: Int64 1
            3: Int64 1
    3: LineNumberNode
      line: Int64 3
      file: Symbol REPL[16]
    4: Expr
      head: Symbol =
      args: Array{Any}((2,))
        1: Symbol b
        2: Expr
          head: Symbol call
          args: Array{Any}((3,))
            1: Symbol +
            2: Symbol a
            3: Int64 4

```

Here the `LineNumberNode` is not interesting, but what we see is that we just have an expression with `head` being `:block`, and the remaining expressions are in the `args`. So if you have an array with expressions you could probably do something along the lines of

```julia
macro mymacro(args...)
    exprs = preprocess(args) # Whatever you do to create the expression list
    Expr(:block, exprs...) # Create a block expression with all sub-expressions
end

```

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<div class="post-metadata">

**Author:** ![Jakub\_Mitura](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jakub_mitura/32/19496_2.png) [@Jakub\_Mitura](https://discourse.julialang.org/u/Jakub_Mitura)\
**Post date:** [October 5, 2021, 3:12pm UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/3 "2021-10-05T15:12:30Z")

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This works very well thank you @albheim  
Just one more thing before and after this list of expression i want to put the while and end  
so I want to add this while and end as expression - yet I get the error in both cases - so i suppose I need somehow escape while and end phrases but how to do this?

push!(tmp, quote while($offsetIter \<32) end)  
push…  
push!(tmp, quote end end)

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<div class="post-metadata">

**Author:** ![albheim](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albheim/32/34660_2.png) [@albheim](https://discourse.julialang.org/u/albheim)\
**Post date:** [October 5, 2021, 4:03pm UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/4 "2021-10-05T16:03:46Z")

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So what you want the macro to generate in the end is something like this?

```julia
while condition
    expr1
    expr2
    ...
end

```

I would suggest to continue with the same approach as I hinted to before, i.e. just have a look at how

```julia
julia> a = quote
       while 3 < 4
       1+1
       end
       end
quote
    #= REPL[1]:2 =#
    while 3 < 4
        #= REPL[1]:3 =#
        1 + 1
    end
end

julia> dump(a)
Expr
  head: Symbol block
  args: Array{Any}((2,))
    1: LineNumberNode
      line: Int64 2
      file: Symbol REPL[1]
    2: Expr
      head: Symbol while
      args: Array{Any}((2,))
        1: Expr
          head: Symbol call
          args: Array{Any}((3,))
            1: Symbol <
            2: Int64 3
            3: Int64 4
        2: Expr
          head: Symbol block
          args: Array{Any}((2,))
            1: LineNumberNode
              line: Int64 3
              file: Symbol REPL[1]
            2: Expr
              head: Symbol call
              args: Array{Any}((3,))
                1: Symbol +
                2: Int64 1
                3: Int64 1

```

behaves and generate the same expression. Will probably be something like

```julia
Expr(:while, Expr(:call, :<, :offsetIter, 32), Expr(:block, exprs...))

```

but you might have to think about what scope offsetIter exists and whether it need escaping or similar.

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<div class="post-metadata">

**Author:** ![Mason](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mason/32/2423_2.png) [@Mason](https://discourse.julialang.org/u/Mason)\
**Post date:** [October 5, 2021, 5:33pm UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/5 "2021-10-05T17:33:22Z")

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> [@Jakub\_Mitura](#):
>
> i have array of expressions generated in macro and i want to return it all so they will be executed one by one

I answered this question yesterday on Slack when you asked this there by the way

 ![image](https://global.discourse-cdn.com/julialang/original/3X/9/2/928899ae282e90f86bb7a06c52be78802395c55d.jpeg)

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<div class="post-metadata">

**Author:** ![Jakub\_Mitura](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jakub_mitura/32/19496_2.png) [@Jakub\_Mitura](https://discourse.julialang.org/u/Jakub_Mitura)\
**Post date:** [October 5, 2021, 6:47pm UTC](https://discourse.julialang.org/t/can-i-concatenate-expressions-in-macro/69220/6 "2021-10-05T18:47:36Z")

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Oh sorry I thought it was so far behind it would not be seen