Can I concatenate expressions in macro?

General Usage
2

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

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

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
1 Like