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[WIP] Create wildcard dimensions for zero(::Type) #77

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[WIP] Create wildcard dimensions for zero(::Type) #77

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1 change: 1 addition & 0 deletions src/DynamicQuantities.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ include("internal_utils.jl")
include("fixed_rational.jl")
include("types.jl")
include("utils.jl")
include("wildcard.jl")
include("math.jl")
include("arrays.jl")
include("units.jl")
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2 changes: 1 addition & 1 deletion src/math.jl
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Expand Up @@ -25,7 +25,7 @@ for (type, base_type, _) in ABSTRACT_QUANTITY_TYPES, op in (:+, :-)
@eval begin
function Base.$op(l::$type, r::$type)
dimension(l) == dimension(r) || throw(DimensionError(l, r))
return new_quantity(typeof(l), $op(ustrip(l), ustrip(r)), dimension(l))
return new_quantity(typeof(l), $op(ustrip(l), ustrip(r)), combine_dimension_with_wildcard(l, r))
end
function Base.$op(l::$type, r::$base_type)
iszero(dimension(l)) || throw(DimensionError(l, r))
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1 change: 0 additions & 1 deletion src/utils.jl
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Expand Up @@ -135,7 +135,6 @@ Base.one(::D) where {D<:AbstractDimensions} = one(D)
# Additive identities (zero)
Base.zero(q::Q) where {Q<:UnionAbstractQuantity} = new_quantity(Q, zero(ustrip(q)), dimension(q))
Base.zero(::AbstractDimensions) = error("There is no such thing as an additive identity for a `AbstractDimensions` object, as + is only defined for `UnionAbstractQuantity`.")
Base.zero(::Type{<:UnionAbstractQuantity}) = error("Cannot create an additive identity for a `UnionAbstractQuantity` type, as the dimensions are unknown. Please use `zero(::UnionAbstractQuantity)` instead.")
Base.zero(::Type{<:AbstractDimensions}) = error("There is no such thing as an additive identity for a `AbstractDimensions` type, as + is only defined for `UnionAbstractQuantity`.")

# Dimensionful 1 (oneunit)
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29 changes: 29 additions & 0 deletions src/wildcard.jl
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@@ -0,0 +1,29 @@
struct WildcardDimensions{R} <: AbstractDimensions{R}
# We simply choose Bool since it will get promoted
WildcardDimensions() = new{Bool}()
end

constructorof(::Type{<:WildcardDimensions}) = WildcardDimensions
dimension_names(::Type{<:WildcardDimensions}) = ()

# Wildcard dimensions are always compatible:
Base.:(==)(::AbstractDimensions, ::WildcardDimensions) = true
Base.:(==)(::WildcardDimensions, ::AbstractDimensions) = true

# For any zero/oneunit specified on the type, we return a wildcard dimension instead:
Base.zero(::Type{Q}) where {T,Q<:UnionAbstractQuantity{T}} = constructorof(Q)(zero(T), WildcardDimensions())
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@gaurav-arya gaurav-arya Nov 2, 2023 •
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I wonder if the right type for the returned value should be along the lines of Quantity{T, Union{WildcardDimensions, Dimensions}}. So that code such as the below would work:

using DynamicQuantities

x = 1u"ms"
arr = [zero(typeof(x))]
arr[1] = x

(Right now, it gives a StackOverflow error, but I presume that's just because the PR is WIP.)


# For propagation rules, we assume all relevant dimensions are zero
Base.getproperty(::WildcardDimensions, ::Symbol) = zero(Bool)
Base.iszero(::WildcardDimensions) = true
Comment on lines +17 to +18
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@gaurav-arya gaurav-arya Nov 3, 2023 •
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These lines seem too dangerous as discussed. Maybe getproperty should just be replaced with an error: (this is not very carefully considered, just a thought)

Suggested change
Base.getproperty(::WildcardDimensions, ::Symbol) = zero(Bool)
Base.iszero(::WildcardDimensions) = true
Base.getproperty(::WildcardDimensions, ::Symbol) = error("Cannot get dimensions of quantity with WildcardDimensions. This is probably because the quantity was created via `zero(T)` for a type `T <: AbstractQuantity`. Instead, use `zero(x)` where `x` is an `AbstractQuantity` with the desired dimensions.")


# Always promote to the other dimension type:
Base.promote_rule(::Type{D}, ::Type{<:WildcardDimensions}) where {D<:AbstractDimensions} = D

# Other utility rules:
Base.show(io::IO, ::WildcardDimensions) = print(io, "[*]")
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If dimension(x) is printed with x having WildcardDimensions, this looks like an array (totally unimportant since this is WIP, but just writing before I forget)


# + and - will remove wildcard dimensions:
combine_dimension_with_wildcard(q1::UnionAbstractQuantity, q2::UnionAbstractQuantity) = combine_dimension_with_wildcard(dimension(q1), dimension(q2))
combine_dimension_with_wildcard(d::AbstractDimensions, ::AbstractDimensions) = d
combine_dimension_with_wildcard(::WildcardDimensions, d::AbstractDimensions) = d