Multiline generator/ array comprehension proposal

[xtalax]

There are a lot of huge multiline comprehensions in MethodOfLines, as I can't seem to get @rule to work within maps.

For clarity I propose the following:

reduce(vcat,
                    [reduce(vcat,
                            [[@rule *(~~a, $(Differential(x)^d)(u), ~~b) =>
                                    upwind_difference(*(~a..., ~b...), d, Idx(II, s, u, indexmap), s,
                                                      pmap.map[operation(u)][x], depvars, derivweights,
                                                      (x2i(s, u, x), x), u, wind_ufunc, indexmap)
                              for d in (let orders = derivweights.orders[x]
                                            orders[isodd.(orders)]
                                        end)]
                             for x in params(u, s)])
                      for u in depvars])

That the for expression which closes the comprehension be on a newline, aligned with the first character inside the square bracket that begins the comprehension.

Thoughts?