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feat: add some missing rational function field functionality #1995

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Merged
merged 1 commit into from
Feb 13, 2025
Merged

feat: add some missing rational function field functionality #1995

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2 changes: 1 addition & 1 deletion src/RationalFunctionField.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
#
###############################################################################

function rational_function_field(k::Field, s::VarName; cached::Bool=true)
function rational_function_field(k::Field, s::VarName = :t; cached::Bool=true)
return Generic.rational_function_field(k, Symbol(s); cached=cached)
end

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10 changes: 6 additions & 4 deletions src/generic/RationalFunctionField.jl
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Expand Up @@ -34,10 +34,6 @@ function is_exact_type(a::Type{S}) where {T <: FieldElement, U <: Union{PolyRing
return is_exact_type(T)
end

function characteristic(R::RationalFunctionField)
return characteristic(base_ring(R))
end

###############################################################################
#
# Constructors
Expand Down Expand Up @@ -127,6 +123,12 @@ function deepcopy_internal(a::RationalFunctionFieldElem, dict::IdDict)
return R(deepcopy_internal(data(a), dict))
end

function characteristic(R::RationalFunctionField)
return characteristic(base_ring(R))
end

is_finite(R::RationalFunctionField) = false

###############################################################################
#
# Canonicalisation
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9 changes: 9 additions & 0 deletions test/generic/RationalFunctionField-test.jl
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Expand Up @@ -6,6 +6,7 @@ end
@testset "Generic.RationalFunctionField.constructors" begin
# Univariate

T, x = rational_function_field(QQ) # verify default variable name is provided
T, x = rational_function_field(QQ, "x")

@test rational_function_field(QQ, "x", cached = true)[1] === rational_function_field(QQ, "x", cached = true)[1]
Expand Down Expand Up @@ -75,6 +76,14 @@ end
@test isa(12//(y + 2), Generic.RationalFunctionFieldElem)

@test isa(((x + 1)//(y + 2))//((y + 3)//(x + 4)), Generic.RationalFunctionFieldElem)

T, = rational_function_field(QQ)
@test characteristic(T) == 0
@test !is_finite(T)

T, = rational_function_field(GF(3))
@test characteristic(T) == 3
@test !is_finite(T)
end

@testset "Generic.RationalFunctionField.printing" begin
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