Incorrect broadcasted Period subtraction behaviour?

[GordStephen]

The behaviour for broadcasted Period subtraction is currently

julia> Day(1) - [Day(2), Day(3)]
2-element Array{Base.Dates.Day,1}:
 1 day 
 2 days

and

julia> Day(1) .- [Day(2), Day(3)]
2-element Array{Base.Dates.Day,1}:
 1 day 
 2 days

whereas presumably the desired output is:

julia> [Day(1) - Day(2), Day(1) - Day(3)]
2-element Array{Base.Dates.Day,1}:
 -1 day 
 -2 days

Looking at dates/periods.jl, the first two method definitions here work fine for + but not -:

for op in (:.+, :.-)
op_ = symbol(string(op)[2:end])
    @eval begin
        ($op){P<:Period}(x::P,Y::StridedArray{P}) = ($op)(Y,x)
        ($op_){P<:Period}(x::P,Y::StridedArray{P}) = ($op)(Y,x)
        ($op_){P<:Period}(Y::StridedArray{P},x::P) = ($op)(Y,x)
    end
end

One option might be to implement unary addition (as identity) and then do

for op in (:.+, :.-)
op_ = symbol(string(op)[2:end])
    @eval begin
        ($op){P<:Period}(x::P,Y::StridedArray{P}) = ($op_)(($op)(Y,x))
        ($op_){P<:Period}(x::P,Y::StridedArray{P}) = ($op_)(($op)(Y,x))
        ($op_){P<:Period}(Y::StridedArray{P},x::P) = ($op)(Y,x)
    end
end

or, just hardcode the definitions as

(.+){P<:Period}(x::P,Y::StridedArray{P}) = Y .+ x
(+){P<:Period}(x::P,Y::StridedArray{P}) = Y .+ x
(+){P<:Period}(Y::StridedArray{P},x::P) = Y .+ x
(.-){P<:Period}(x::P,Y::StridedArray{P}) = (-Y) .+ x
(-){P<:Period}(x::P,Y::StridedArray{P}) = (-Y) .+ x
(-){P<:Period}(Y::StridedArray{P},x::P) = Y .- x

which would actually be fewer LOC... maybe more readable too.

[GordStephen]

I'm working on a PR to get addition/subtraction working with heterogeneous Period arrays right now, so I'm happy to fix this while I'm at it - is there a preference between the two approaches mentioned above?

[quinnj]

Closed via #12115