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Change behavior of base_ring for UniversalPolyRing #2182

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ff47594
Change behavior of `base_ring` for `UniversalPolyRing`
SoongNoonien Oct 6, 2025
4ff08ba
Fix `UnivPoly` tests
SoongNoonien Oct 6, 2025
6f8c6f2
Remove `mpoly_ring` for universal polynomial ring
SoongNoonien Oct 9, 2025
ae5b7c3
Update src/generic/UnivPoly.jl
SoongNoonien Oct 20, 2025
3a0ec26
Rename `mpoly_ring` to `base_ring`
SoongNoonien Oct 22, 2025
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2 changes: 1 addition & 1 deletion src/generic/GenericTypes.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -417,7 +417,7 @@ end
###############################################################################

@attributes mutable struct UniversalPolyRing{T <: RingElement} <: AbstractAlgebra.UniversalPolyRing{T}
mpoly_ring::AbstractAlgebra.MPolyRing{T}
base_ring::AbstractAlgebra.MPolyRing{T}

function UniversalPolyRing{T}(
R::Ring, s::Vector{Symbol}, internal_ordering::Symbol, cached::Bool=true
Expand Down
68 changes: 32 additions & 36 deletions src/generic/UnivPoly.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,11 @@
#
###############################################################################

base_ring_type(::Type{<:UniversalPolyRing{T}}) where T = parent_type(T)
base_ring(S::UniversalPolyRing) = base_ring(mpoly_ring(S))::base_ring_type(S)
base_ring_type(::Type{<:UniversalPolyRing{T}}) where T = mpoly_ring_type(T)
base_ring(S::UniversalPolyRing) = S.base_ring::base_ring_type(S)

coefficient_ring_type(T::Type{<:UniversalPolyRing}) = base_ring_type(T)
coefficient_ring(S::UniversalPolyRing) = base_ring(S)
coefficient_ring_type(::Type{<:UniversalPolyRing{T}}) where T = parent_type(T)
coefficient_ring(S::UniversalPolyRing) = coefficient_ring(base_ring(S))::coefficient_ring_type(S)

function is_domain_type(::Type{<:UnivPoly{S}}) where {S <: RingElement}
return is_domain_type(S)
Expand All @@ -30,23 +30,19 @@ elem_type(::Type{UniversalPolyRing{T}}) where {T<:RingElement} = UnivPoly{T}

parent_type(::Type{UnivPoly{T}}) where {T<:RingElement} = UniversalPolyRing{T}

function mpoly_ring(S::UniversalPolyRing{T}) where {T<:RingElement}
return S.mpoly_ring::mpoly_ring_type(T)
end

number_of_variables(S::UniversalPolyRing) = number_of_variables(mpoly_ring(S))
number_of_variables(S::UniversalPolyRing) = number_of_variables(base_ring(S))

number_of_generators(S::UniversalPolyRing) = number_of_generators(mpoly_ring(S))
number_of_generators(S::UniversalPolyRing) = number_of_generators(base_ring(S))

symbols(S::UniversalPolyRing) = symbols(mpoly_ring(S))
symbols(S::UniversalPolyRing) = symbols(base_ring(S))

function vars(p::UnivPoly{T}) where {T}
S = parent(p)
V = vars(data(p))
return [UnivPoly{T}(v, S) for v in V]
end

internal_ordering(p::UniversalPolyRing) = internal_ordering(mpoly_ring(p))
internal_ordering(p::UniversalPolyRing) = internal_ordering(base_ring(p))

data(p::UnivPoly{T}) where {T<:RingElement} = p.p::mpoly_type(T)

Expand Down Expand Up @@ -84,7 +80,7 @@ function coeff(p::UnivPoly, exps::Vector{Int})
n = nvars(parent(data(p)))
if len > n
if !iszero(exps[n + 1:len])
return base_ring(S)()
return coefficient_ring(S)()
end
return coeff(data(p), exps[1:n])
end
Expand All @@ -96,7 +92,7 @@ function coeff(p::UnivPoly, exps::Vector{Int})
end

function setcoeff!(p::UnivPoly, exps::Vector{Int}, c::T) where T <: RingElement
c = base_ring(data(p))(c)
c = coefficient_ring(data(p))(c)
S = parent(p)
len = length(exps)
if len != nvars(parent(data(p)))
Expand All @@ -120,9 +116,9 @@ end
#
###############################################################################

zero(R::UniversalPolyRing{T}) where {T} = UnivPoly{T}(zero(mpoly_ring(R)), R)
zero(R::UniversalPolyRing{T}) where {T} = UnivPoly{T}(zero(base_ring(R)), R)

one(R::UniversalPolyRing{T}) where {T} = UnivPoly{T}(one(mpoly_ring(R)), R)
one(R::UniversalPolyRing{T}) where {T} = UnivPoly{T}(one(base_ring(R)), R)

iszero(p::UnivPoly) = iszero(data(p))

Expand Down Expand Up @@ -241,7 +237,7 @@ function _ensure_variables(S::UniversalPolyRing, v::Vector{<:VarName})
end
if !isempty(added_symbols)
new_symbols = vcat(current_symbols, added_symbols)
S.mpoly_ring = AbstractAlgebra.polynomial_ring_only(base_ring(S), new_symbols; internal_ordering=internal_ordering(S), cached=false)
S.base_ring = AbstractAlgebra.polynomial_ring_only(coefficient_ring(S), new_symbols; internal_ordering=internal_ordering(S), cached=false)
end
return idx
end
Expand All @@ -252,14 +248,14 @@ function gen(S::UniversalPolyRing, s::VarName)
new_symbols = copy(symbols(S))
push!(new_symbols, Symbol(s))
i = length(new_symbols)
S.mpoly_ring = AbstractAlgebra.polynomial_ring_only(base_ring(S), new_symbols; internal_ordering=internal_ordering(S), cached=false)
S.base_ring = AbstractAlgebra.polynomial_ring_only(coefficient_ring(S), new_symbols; internal_ordering=internal_ordering(S), cached=false)
end
return @inbounds gen(S, i)
end

function gen(S::UniversalPolyRing{T}, i::Int) where {T}
@boundscheck 1 <= i <= nvars(S) || throw(ArgumentError("generator index out of range"))
return UnivPoly{T}(gen(mpoly_ring(S), i), S)
return UnivPoly{T}(gen(base_ring(S), i), S)
end

function gens(S::UniversalPolyRing{T}) where {T}
Expand All @@ -273,7 +269,7 @@ function _univ_poly_gens(S::UniversalPolyRing{T}, vars::Vector{Symbol}) where {T
idx = _ensure_variables(S, vars)
# TRICK: @varnames_interface expects two return values, but we only care
# for the second; so just return literally nothing for the first
return nothing, [UnivPoly{T}(gen(mpoly_ring(S), i), S) for i in idx]
return nothing, [UnivPoly{T}(gen(base_ring(S), i), S) for i in idx]
end

AbstractAlgebra.@varnames_interface _univ_poly_gens(R::UniversalPolyRing{T}, s) where {T}
Expand All @@ -294,7 +290,7 @@ end

canonical_unit(p::UnivPoly) = canonical_unit(data(p))

characteristic(R::UniversalPolyRing) = characteristic(base_ring(R))
characteristic(R::UniversalPolyRing) = characteristic(coefficient_ring(R))

function Base.hash(p::UnivPoly, h::UInt)
b = 0xcf418d4529109236%UInt
Expand Down Expand Up @@ -357,7 +353,7 @@ function show(io::IO, R::UniversalPolyRing)
@show_name(io, R)
@show_special(io, R)
print(io, "Universal Polynomial Ring over ")
show(io, base_ring(R))
show(io, coefficient_ring(R))
end

function expressify(a::UnivPoly, x = symbols(parent(a)); context = nothing)
Expand Down Expand Up @@ -788,7 +784,7 @@ end
###############################################################################

function evaluate(a::UnivPoly{T}, A::Vector{T}) where {T <: RingElem}
R = base_ring(a)
R = coefficient_ring(a)
n = length(A)
num = nvars(parent(data(a)))
if n > num
Expand Down Expand Up @@ -832,7 +828,7 @@ function evaluate(a::UnivPoly{T}, A::Vector{V}) where {T <: RingElement, V <: Ri
end
if n < num
if n == 0
R = base_ring(a)
R = coefficient_ring(a)
return evaluate(data(a), [zero(R) for _ in 1:num])
else
R = parent(A[1])
Expand Down Expand Up @@ -943,7 +939,7 @@ is_univariate(p::UnivPoly) = is_univariate(data(p))

is_univariate_with_data(p::UnivPoly) = is_univariate_with_data(data(p))

is_univariate(R::UniversalPolyRing) = is_univariate(mpoly_ring(R))
is_univariate(R::UniversalPolyRing) = is_univariate(base_ring(R))

function coefficients_of_univariate(p::UnivPoly, check_univariate::Bool=true)
return coefficients_of_univariate(data(p), check_univariate)
Expand All @@ -958,7 +954,7 @@ end
_change_univ_poly_ring(R, Rx, cached::Bool) = universal_polynomial_ring(R, symbols(Rx); internal_ordering=internal_ordering(Rx), cached)[1]

function change_base_ring(R::Ring, p::UnivPoly{T}; cached::Bool=true, parent::UniversalPolyRing = _change_univ_poly_ring(R, parent(p), cached)) where {T <: RingElement}
base_ring(parent) != R && error("Base rings do not match.")
coefficient_ring(parent) != R && error("Base rings do not match.")
return _map(R, p, parent)
end

Expand All @@ -972,7 +968,7 @@ end
#
################################################################################

function map_coefficients(f::T, p::UnivPoly; cached::Bool=true, parent::UniversalPolyRing = _change_univ_poly_ring(parent(f(zero(base_ring(p)))), parent(p), cached)) where T
function map_coefficients(f::T, p::UnivPoly; cached::Bool=true, parent::UniversalPolyRing = _change_univ_poly_ring(parent(f(zero(coefficient_ring(p)))), parent(p), cached)) where T
return _map(f, p, parent)
end

Expand Down Expand Up @@ -1012,7 +1008,7 @@ RandomExtensions.maketype(S::AbstractAlgebra.UniversalPolyRing, _, _, _) = elem_

function RandomExtensions.make(S::AbstractAlgebra.UniversalPolyRing, term_range::AbstractUnitRange{Int},
exp_bound::AbstractUnitRange{Int}, vs...)
R = base_ring(S)
R = coefficient_ring(S)
if length(vs) == 1 && elem_type(R) == Random.gentype(vs[1])
Make(S, term_range, exp_bound, vs[1])
else
Expand All @@ -1025,7 +1021,7 @@ function rand(rng::AbstractRNG, sp::SamplerTrivial{<:Make4{
S, term_range, exp_bound, v = sp[][1:end]
f = S()
g = gens(S)
R = base_ring(S)
R = coefficient_ring(S)
for i = 1:rand(rng, term_range)
term = S(1)
for j = 1:length(g)
Expand Down Expand Up @@ -1172,7 +1168,7 @@ end

function upgrade(S::UniversalPolyRing{T}, pp::MPolyRingElem{T}) where {T}
n = nvars(S) - nvars(parent(pp))
ctx = MPolyBuildCtx(mpoly_ring(S))
ctx = MPolyBuildCtx(base_ring(S))
v0 = zeros(Int, n)
for (c, v) in zip(coefficients(pp), exponent_vectors(pp))
push_term!(ctx, c, vcat(v, v0))
Expand All @@ -1181,19 +1177,19 @@ function upgrade(S::UniversalPolyRing{T}, pp::MPolyRingElem{T}) where {T}
end

function (a::UniversalPolyRing{T})(b::RingElement) where {T <: RingElement}
return a(base_ring(a)(b))
return a(coefficient_ring(a)(b))
end

function (a::UniversalPolyRing{T})() where {T <: RingElement}
return UnivPoly{T}(mpoly_ring(a)(), a)
return UnivPoly{T}(base_ring(a)(), a)
end

function (a::UniversalPolyRing{T})(b::Union{Integer, Rational, AbstractFloat}) where {T <: RingElement}
return UnivPoly{T}(mpoly_ring(a)(b), a)
return UnivPoly{T}(base_ring(a)(b), a)
end

function (a::UniversalPolyRing{T})(b::T) where {T <: RingElem}
return UnivPoly{T}(mpoly_ring(a)(b), a)
return UnivPoly{T}(base_ring(a)(b), a)
end

function (S::UniversalPolyRing{T})(p::UnivPoly{T}) where {T <: RingElement}
Expand All @@ -1208,12 +1204,12 @@ end
function (a::UniversalPolyRing{T})(b::Vector{T}, m::Vector{Vector{Int}}) where {T <: RingElement}
if length(m) != 0
len = length(m[1])
num = nvars(mpoly_ring(a))
num = nvars(base_ring(a))
if len != num
for i = 1:length(m)
m[i] = vcat(m[i], zeros(Int, num - len))
end
end
end
return UnivPoly{T}(mpoly_ring(a)(b, m), a)
return UnivPoly{T}(base_ring(a)(b, m), a)
end
16 changes: 8 additions & 8 deletions test/generic/UnivPoly-test.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@
@test elem_type(Generic.UniversalPolyRing{elem_type(R)}) == Generic.UnivPoly{elem_type(R)}
@test parent_type(Generic.UnivPoly{elem_type(R)}) == Generic.UniversalPolyRing{elem_type(R)}

@test base_ring(S) === R
@test coefficient_ring(S) === R
@test coefficient_ring(S) === R
@test coefficient_ring_type(S) === typeof(R)

Expand Down Expand Up @@ -137,10 +137,10 @@ end
@test parent(f2) === S
@test parent(f3) === S

@test base_ring(S) === R
@test base_ring(f1) === R
@test base_ring(f2) === R
@test base_ring(f3) === R
@test coefficient_ring(S) === R
@test coefficient_ring(f1) === R
@test coefficient_ring(f2) === R
@test coefficient_ring(f3) === R

@test nvars(S) == 3

Expand Down Expand Up @@ -1113,9 +1113,9 @@ end
@test length(g) == length(g1)
@test length(h) == length(h1)

@test base_ring(f1) === U
@test base_ring(g1) === U
@test base_ring(h1) === U
@test coefficient_ring(f1) === U
@test coefficient_ring(g1) === U
@test coefficient_ring(h1) === U

f2 = map_coefficients(x->x^2, f)
g2 = map_coefficients(x->x^2, g)
Expand Down
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