allowing assignments to the right at the end of a chain

[pfarndt]

I use DataFramesMeta in Jupyter Notebooks for data analysis a lot. I prefer to develop some chain of where/select etc functions, like:

@linq data |>
  where(...) |>
  where(...) 

During development of such a workflow I usually have a first(5) at the end to check everything works ok, like:

@linq data |>
  where(...) |>
  where(...) |>
  first(5)

If everything is fine I want to the resulting data "flow" into a new variable. In principle I can do either:

newdata = @linq data |>
  where(...) |>
  where(...) 

or

@linq data |>
  where(...) |>
  where(...) 
newdata = ans

Both are not optimal. In the first version the newdata is at the very beginning of the expression, the second uses the ans variable. Ideally I would like to be able to assign to the right using some special operator (e.g. |>=), like:

@linq data |>
  where(...) |>
  where(...) |>= newdata

Would this be conceivable?

[pdeffebach]

I agree this would be a cool thing to have. I hate it when I write a long chain and then have to go back to the top.

I think if this feature is able to be added, it wouldn't have much to do with DataFramesMeta, and would be general.

On top of this, I think it's increasingly likely that @linq will be deprecated in favor of a dependency on Chain.jl.

Ill take a look at some options and see what's possible with macros.

[pdeffebach]

It looks like this is possible, for the most part, with Chain.jl

julia> using DataFramesMeta;

julia> df = DataFrame(a = [1, 2]);

julia> @chain df begin 
           @transform(y = :a)
           newdata = _
       end
2×2 DataFrame
 Row │ a      y     
     │ Int64  Int64 
─────┼──────────────
   1 │     1      1
   2 │     2      2

So this feature will be "added" if we deprecate @linq in favor of @chain

[pdeffebach]

Wait, that example doesn't actually work. I will still think about this.