Add default zero behaviour for Fourier spaces

Author: OlivierHnt

src/sequence_spaces/sequence.jl

@@ -110,6 +110,7 @@ Base.zero(a::Sequence) = zeros(eltype(a), space(a))
 Base.zero(::Type{Sequence{T,S}}) where {T<:VectorSpace,S<:AbstractVector} = zeros(eltype(S), _zero_space(T))
 _zero_space(::Type{TensorSpace{T}}) where {T<:Tuple} = TensorSpace(map(_zero_space, fieldtypes(T)))
 _zero_space(::Type{Taylor}) = Taylor(0)
+_zero_space(::Type{Fourier{T}}) where {T<:Real} = Fourier(0, one(T))
 _zero_space(::Type{Chebyshev}) = Chebyshev(0)
 
 Base.one(a::Sequence{ParameterSpace}) = Sequence(space(a), [one(eltype(a))])

src/sequence_spaces/symmetry.jl

@@ -113,6 +113,8 @@ IntervalArithmetic.interval(s::CosFourier) = CosFourier(interval(desymmetrize(s)
 
 _prettystring(s::CosFourier) = "CosFourier(" * string(order(s)) * ", " * string(frequency(s)) * ", " * string(multiple(s)) * ")"
 
+_zero_space(::Type{CosFourier{T}}) where {T<:Real} = CosFourier(0, one(T))
+
 
 
 struct SinFourier{T<:Real} <: SymBaseSpace
@@ -155,6 +157,8 @@ IntervalArithmetic.interval(s::SinFourier) = SinFourier(interval(desymmetrize(s)
 
 _prettystring(s::SinFourier) = "SinFourier(" * string(order(s)) * ", " * string(frequency(s)) * ", " * string(multiple(s)) * ")"
 
+_zero_space(::Type{SinFourier{T}}) where {T<:Real} = SinFourier(1, one(T))
+