add partype method to lognormal and semicircle (#1773)

* add partype method to lognormal and semicircle

* Update src/univariate/continuous/lognormal.jl

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

* Update src/univariate/continuous/semicircle.jl

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

* add tests on par_type and Float32

* adapt partype testing to special case

of nothing parameters

and fix warning on ambiguous global variable

* breaking adapt tests of special cases: Int partype

* LocationScale: do not promote T

but promote eltype T with eltype(inner)
but also promote partype T with partype(inner)

* Update .gitignore

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

* revert DiscreteUniform to non-parametric

will be moved to its own pull-request

* generalize check of partype for non-Real parameters

e.g. Nothing in Truncated distribution

* Update src/univariate/locationscale.jl

D is not used inside the function any more -> can simpify

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

* Remove comments

* Apply suggestions from code review

---------

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

Author: bgctw

src/univariate/continuous/lognormal.jl

@@ -62,6 +62,7 @@ stdlogx(d::LogNormal) = d.σ
 mean(d::LogNormal) = ((μ, σ) = params(d); exp(μ + σ^2/2))
 median(d::LogNormal) = exp(d.μ)
 mode(d::LogNormal) = ((μ, σ) = params(d); exp(μ - σ^2))
+partype(::LogNormal{T}) where {T<:Real} = T
 
 function var(d::LogNormal)
     (μ, σ) = params(d)

src/univariate/continuous/semicircle.jl

@@ -34,6 +34,7 @@ Semicircle(r::Integer; check_args::Bool=true) = Semicircle(float(r); check_args=
 @distr_support Semicircle -d.r +d.r
 
 params(d::Semicircle) = (d.r,)
+partype(::Semicircle{T}) where {T<:Real} = T
 
 mean(d::Semicircle) = zero(d.r)
 var(d::Semicircle) = d.r^2 / 4

src/univariate/discrete/discreteuniform.jl

@@ -42,6 +42,8 @@ span(d::DiscreteUniform) = d.b - d.a + 1
 probval(d::DiscreteUniform) = d.pv
 params(d::DiscreteUniform) = (d.a, d.b)
 
+partype(::DiscreteUniform) = Int
+
 ### Show
 
 show(io::IO, d::DiscreteUniform) = show(io, d, (:a, :b))

src/univariate/discrete/hypergeometric.jl

@@ -38,6 +38,7 @@ end
 
 @distr_support Hypergeometric max(d.n - d.nf, 0) min(d.ns, d.n)
 
+partype(::Hypergeometric) = Int
 
 ### Parameters
 

src/univariate/locationscale.jl

@@ -51,8 +51,9 @@ end
 
 function AffineDistribution(μ::T, σ::T, ρ::UnivariateDistribution; check_args::Bool=true) where {T<:Real}
     @check_args AffineDistribution (σ, !iszero(σ))
-    _T = promote_type(eltype(ρ), T)
-    return AffineDistribution{_T}(_T(μ), _T(σ), ρ)
+    # μ and σ act on both random numbers and parameter-like quantities like mean
+    # hence do not promote: but take care in eltype and partype
+    return AffineDistribution{T}(μ, σ, ρ)
 end
 
 function AffineDistribution(μ::Real, σ::Real, ρ::UnivariateDistribution; check_args::Bool=true)
@@ -71,7 +72,7 @@ end
 const ContinuousAffineDistribution{T<:Real,D<:ContinuousUnivariateDistribution} = AffineDistribution{T,Continuous,D}
 const DiscreteAffineDistribution{T<:Real,D<:DiscreteUnivariateDistribution} = AffineDistribution{T,Discrete,D}
 
-Base.eltype(::Type{<:AffineDistribution{T}}) where T = T
+Base.eltype(::Type{<:AffineDistribution{T,S,D}}) where {T,S,D} = promote_type(eltype(D), T)
 
 minimum(d::AffineDistribution) =
     d.σ > 0 ? d.μ + d.σ * minimum(d.ρ) : d.μ + d.σ * maximum(d.ρ)
@@ -102,7 +103,7 @@ Base.convert(::Type{AffineDistribution{T}}, d::AffineDistribution{T}) where {T<:
 location(d::AffineDistribution) = d.μ
 scale(d::AffineDistribution) = d.σ
 params(d::AffineDistribution) = (d.μ,d.σ,d.ρ)
-partype(::AffineDistribution{T}) where {T} = T
+partype(d::AffineDistribution{T}) where {T} = promote_type(partype(d.ρ), T)
 
 #### Statistics
 

test/univariate/locationscale.jl

@@ -117,7 +117,7 @@ function test_location_scale(
                 rand!(rng, dtest, r)
             end
             @test mean(r) ≈ mean(dref) atol=0.02
-            @test std(r) ≈ std(dref) atol=0.01
+            @test std(r) ≈ std(dref) atol=0.02
             @test cf(dtest, -0.1) ≈ cf(dref,-0.1)
 
             if dref isa ContinuousDistribution

test/univariates.jl

@@ -62,6 +62,11 @@ function verify_and_test(D::Union{Type,Function}, d::UnivariateDistribution, dct
     # test various constructors for promotion, all-Integer args, etc.
     pars = params(d)
 
+    # verify parameter type
+    # truncated parameters may be nothing
+    @test partype(d) === mapfoldl(
+        typeof, (S, T) -> T <: Distribution ? promote_type(S, partype(T)) : (T <: Nothing ? S : promote_type(S, eltype(T))), pars; init = Union{})
+    
     # promotion constructor:
     float_pars = map(x -> isa(x, AbstractFloat), pars)
     if length(pars) > 1 && sum(float_pars) > 1 && !isa(D, typeof(truncated))

test/utils.jl

@@ -15,8 +15,10 @@ r = RealInterval(1.5, 4.0)
 
 # special cases
 @test partype(Kolmogorov()) == Float64
-@test partype(Hypergeometric(2, 2, 2)) == Float64
-@test partype(DiscreteUniform(0, 4)) == Float64
+@test partype(Hypergeometric(2, 2, 2)) == Int
+@test partype(Hypergeometric(2.0, 2, 2)) == Int
+@test partype(DiscreteUniform(0, 4)) == Int
+@test partype(DiscreteUniform(0.0, 4)) == Int
 
 A = rand(1:10, 5, 5)
 B = rand(Float32, 4)