zero for OneElement

[jishnub]

With this,

julia> v = OneElement(10, 3, 4)
4-element OneElement{Int64, 1, Tuple{Int64}, Tuple{Base.OneTo{Int64}}}:
  ⋅
  ⋅
 10
  ⋅

julia> zero(v)
4-element Zeros{Int64}

julia> v + zero(v) isa typeof(v)
true

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.90%. Comparing base (4bfbeec) to head (af63448).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #332   +/-   ##
=======================================
  Coverage   99.90%   99.90%           
=======================================
  Files           8        8           
  Lines        1086     1093    +7     
=======================================
+ Hits         1085     1092    +7     
  Misses          1        1           

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[longemen3000]

Seems good to add. But before adding, what is the contract for zero when using with AbstractArray?. before merging, is there any advantage on returning Zeros{T}/Ones{T} instead of OneElement{T} ?

[jishnub]

The main advantage is that typeof(x + zero(x)) will be the same as typeof(x), in this case a OneElement. The sum of two OneElements isn't a OneElement.

[jishnub]

I've updated this to return a zero based on the value and not the type. zero(v::OneElement) now tries to preserve the type of the array, which is often assumed elsewhere.

julia> using FillArrays

julia> v = OneElement(10, 3, 4)
4-element OneElement{Int64, 1, Tuple{Int64}, Tuple{Base.OneTo{Int64}}}:
  ⋅
  ⋅
 10
  ⋅

julia> zero(v)
4-element OneElement{Int64, 1, Tuple{Int64}, Tuple{Base.OneTo{Int64}}}:
 ⋅
 ⋅
 0
 ⋅

[jishnub]

Gentle bump