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Add isonebased trait to opt out of OffsetArray wrappers #335

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Add isonebased trait to opt out of OffsetArray wrappers #335

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49c463b
Add isonebased trait to opt-out of OffsetArray wrappers
jishnub Jul 3, 2023
c38d76e
use isonebased in similar(::Type{<:AbstractArray}, ax...)
jishnub Jul 3, 2023
71565b6
dispatch on types, and add tests
jishnub Jul 4, 2023
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Add isonebased trait to opt-out of OffsetArray wrappers
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@jishnub
jishnub committed Jul 3, 2023
commit 49c463b7c28e1a2494f6d136a32be22a0e6facd9
46 changes: 33 additions & 13 deletions src/OffsetArrays.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -317,15 +317,35 @@ end

Base.similar(A::OffsetArray, ::Type{T}, dims::Dims) where T =
similar(parent(A), T, dims)

"""
isonebased(ax::AbstractUnitRange{<:Integer})

Return whether `firstindex(ax)` is statically known to be `1`. Custom axis types may extend this method
to ensure that the axis offset is ignored, for example in `similar`.
"""
isonebased(_) = false
isonebased(::Integer) = true
isonebased(::Base.OneTo) = true
isonebased(::IIUR{<:Base.OneTo}) = true

to_length(i::Integer) = i
to_length(i::AbstractUnitRange) = length(i)

# Since the following is committing type-piracy, we provide an opt-out mechanism to the users
function Base.similar(A::AbstractArray, ::Type{T}, shape::Tuple{OffsetAxisKnownLength,Vararg{OffsetAxisKnownLength}}) where T
# strip IdOffsetRanges to extract the parent range and use it to generate the array
new_shape = map(_strip_IdOffsetRange, shape)
# route through _similar_axes_or_length to avoid a stack overflow if map(_strip_IdOffsetRange, shape) === shape
# This tries to use new_shape directly in similar if similar(A, T, ::typeof(new_shape)) is defined
# If this fails, it calls similar(A, T, map(_indexlength, new_shape)) to use the size along each axis
# to generate the new array
P = _similar_axes_or_length(A, T, new_shape, shape)
return OffsetArray(P, map(_offset, axes(P), shape))
if all(isonebased, shape)
return similar(A, T, map(to_length, shape))
else
# strip IdOffsetRanges to extract the parent range and use it to generate the array
new_shape = map(_strip_IdOffsetRange, shape)
# route through _similar_axes_or_length to avoid a stack overflow if map(_strip_IdOffsetRange, shape) === shape
# This tries to use new_shape directly in similar if similar(A, T, ::typeof(new_shape)) is defined
# If this fails, it calls similar(A, T, map(_indexlength, new_shape)) to use the size along each axis
# to generate the new array
P = _similar_axes_or_length(A, T, new_shape, shape)
return OffsetArray(P, map(_offset, axes(P), shape))
end
end
Base.similar(::Type{A}, sz::Tuple{Vararg{Int}}) where {A<:OffsetArray} = similar(Array{eltype(A)}, sz)
function Base.similar(::Type{T}, shape::Tuple{OffsetAxisKnownLength,Vararg{OffsetAxisKnownLength}}) where {T<:AbstractArray}
Expand Down Expand Up @@ -699,11 +719,11 @@ no_offset_view(a::Array) = a
no_offset_view(i::Number) = i
no_offset_view(A::AbstractArray) = _no_offset_view(axes(A), A)
_no_offset_view(::Tuple{}, A::AbstractArray{T,0}) where T = A
_no_offset_view(::Tuple{Base.OneTo, Vararg{Base.OneTo}}, A::AbstractArray) = A
# the following method is needed for ambiguity resolution
_no_offset_view(::Tuple{Base.OneTo, Vararg{Base.OneTo}}, A::AbstractUnitRange) = A
_no_offset_view(::Any, A::AbstractArray) = OffsetArray(A, Origin(1))
_no_offset_view(::Any, A::AbstractUnitRange) = UnitRange(A)
function _no_offset_view(ax::Tuple, A::AbstractArray)
all(isonebased, ax) ? A : __no_offset_view(A)
end
__no_offset_view(A::AbstractArray) = OffsetArray(A, Origin(1))
__no_offset_view(A::AbstractUnitRange) = UnitRange(A)

#####
# center/centered
Expand Down