Add missing file

Author: mtfishman

src/linearcombination.jl

@@ -0,0 +1,92 @@
+using Base.Broadcast: Broadcasted
+struct LinearCombination{C} <: Function
+  coefficients::C
+end
+coefficients(a::LinearCombination) = a.coefficients
+function (f::LinearCombination)(args...)
+  return mapreduce(*,+,coefficients(f),args)
+end
+
+struct Sum{Style,C<:Tuple,A<:Tuple}
+  style::Style
+  coefficients::C
+  arguments::A
+end
+coefficients(a::Sum) = a.coefficients
+arguments(a::Sum) = a.arguments
+style(a::Sum) = a.style
+LinearCombination(a::Sum) = LinearCombination(coefficients(a))
+using Base.Broadcast: combine_axes
+Base.axes(a::Sum) = combine_axes(a.arguments...)
+function Base.eltype(a::Sum)
+  cts = typeof.(coefficients(a))
+  elts = eltype.(arguments(a))
+  ts = map((ct, elt) -> Base.promote_op(*, ct, elt), cts, elts)
+  return Base.promote_op(+, ts...)
+end
+using Base.Broadcast: combine_styles
+function Sum(coefficients::Tuple, arguments::Tuple)
+  return Sum(combine_styles(arguments...), coefficients, arguments)
+end
+Sum(a) = Sum((one(eltype(a)),), (a,))
+function Base.:+(a::Sum, b::Sum)
+  return Sum((coefficients(a)..., coefficients(b)...), (arguments(a)..., arguments(b)...))
+end
+Base.:-(a::Sum, b::Sum) = a + (-b)
+Base.:+(a::Sum, b::AbstractArray) = a + Sum(b)
+Base.:-(a::Sum, b::AbstractArray) = a - Sum(b)
+Base.:+(a::AbstractArray, b::Sum) = Sum(a) + b
+Base.:-(a::AbstractArray, b::Sum) = Sum(a) - b
+Base.:*(c::Number, a::Sum) = Sum(c .* coefficients(a), arguments(a))
+Base.:*(a::Sum, c::Number) = c * a
+Base.:/(a::Sum, c::Number) = Sum(coefficients(a) ./ c, arguments(a))
+Base.:-(a::Sum) = -1 * a
+
+function Base.copy(a::Sum)
+  return copyto!(similar(a), a)
+end
+Base.similar(a::Sum) = similar(a, eltype(a))
+Base.similar(a::Sum, elt::Type) = similar(a, elt, axes(a))
+function Base.copyto!(dest::AbstractArray, a::Sum)
+  f = LinearCombination(a)
+  dest .= f.(arguments(a)...)
+  return dest
+end
+function Broadcast.Broadcasted(a::Sum)
+  f = LinearCombination(a)
+  return Broadcasted(style(a), f, arguments(a), axes(a))
+end
+function Base.similar(a::Sum, elt::Type, ax::Tuple)
+  return similar(Broadcasted(a), elt, ax)
+end
+
+using Base.Broadcast: Broadcast, AbstractArrayStyle, DefaultArrayStyle
+Broadcast.materialize(a::Sum) = copy(a)
+Broadcast.materialize!(dest, a::Sum) = copyto!(dest, a)
+struct SumStyle <: AbstractArrayStyle{Any} end
+Broadcast.broadcastable(a::Sum) = a
+Broadcast.BroadcastStyle(::Type{<:Sum}) = SumStyle()
+Broadcast.BroadcastStyle(style::SumStyle, ::AbstractArrayStyle) = style
+# Fix ambiguity error with Base.
+Broadcast.BroadcastStyle(style::SumStyle, ::DefaultArrayStyle) = style
+function Broadcast.broadcasted(::SumStyle, f, as...)
+  return error("Arbitrary broadcasting not supported for SumStyle.")
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(+), a, b::Sum)
+  return Sum(a) + b
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(+), a::Sum, b)
+  return a + Sum(b)
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(+), a::Sum, b::Sum)
+  return a + b
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(*), c::Number, a)
+  return c * Sum(a)
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(*), c::Number, a::Sum)
+  return c * a
+end
+function Broadcast.broadcasted(::SumStyle, ::typeof(/), a::Sum, c::Number)
+  return Sum(a) / c
+end