bugfix in weighted measures (#13)

* bugfix in weighted measures

* Canonical structure for Affine/Weighted composition

* bump version

Author: cscherrer

Project.toml

@@ -1,7 +1,7 @@
 name = "MeasureBase"
 uuid = "fa1605e6-acd5-459c-a1e6-7e635759db14"
 authors = ["Chad Scherrer <[email protected]> and contributors"]
-version = "0.3.6"
+version = "0.3.7"
 
 [deps]
 ConcreteStructs = "2569d6c7-a4a2-43d3-a901-331e8e4be471"

src/MeasureBase.jl

@@ -49,8 +49,8 @@ include("primitives/lebesgue.jl")
 include("primitives/dirac.jl")
 include("primitives/trivial.jl")
 
-include("combinators/affine.jl")
 include("combinators/weighted.jl")
+include("combinators/affine.jl")
 include("combinators/superpose.jl")
 include("combinators/product.jl")
 include("combinators/for.jl")

src/combinators/affine.jl

@@ -4,6 +4,8 @@ struct AffineTransform{N,T}
     par::NamedTuple{N,T}
 end
 
+params(f::AffineTransform) = getfield(f, :par)
+
 @inline Base.getproperty(d::AffineTransform, s::Symbol) = getfield(getfield(d, :par), s)
 
 Base.propertynames(d::AffineTransform{N}) where {N} = N 
@@ -25,6 +27,12 @@ Base.propertynames(d::AffineTransform{N}) where {N} = N
 struct Affine{N,M,T} <: AbstractMeasure
     f::AffineTransform{N,T}
     parent::M
+
+    function Affine(f::AffineTransform, parent::WeightedMeasure)
+        WeightedMeasure(parent.logweight, Affine(f, parent.base))
+    end
+
+    Affine(f::AffineTransform{N,T}, parent::M) where {N,M,T} = new{N,M,T}(f, parent)
 end
 
 parent(d::Affine) = getfield(d, :parent)

src/combinators/half.jl

@@ -17,4 +17,4 @@ function Base.rand(rng::AbstractRNG, T::Type, μ::Half)
     return abs(rand(rng, T, unhalf(μ)))
 end
 
-logdensity(μ::Half, x) = (x < 0) * (-Inf) + (x > 0) * logdensity(unhalf(μ), x)
+logdensity(μ::Half, x) = x > 0 ? logdensity(unhalf(μ), x) : -Inf

src/combinators/weighted.jl

@@ -22,6 +22,14 @@ end
 struct WeightedMeasure{R,M} <: AbstractWeightedMeasure
     logweight :: R
     base :: M
+
+    function WeightedMeasure(ℓ, b::WeightedMeasure)
+        WeightedMeasure(ℓ + b.logweight, b.base)
+    end 
+
+    function WeightedMeasure(ℓ::R, b::M) where {R,M}
+        new{R,M}(ℓ, b)
+    end 
 end
 
 function Base.show(io::IO, μ::WeightedMeasure)
@@ -43,7 +51,7 @@ end
 
 function Base.:*(k::T, m::AbstractMeasure) where {T <: Number}
     logk = log(k)
-    return WeightedMeasure{typeof(logk), typeof(m)}(logk,m)
+    return WeightedMeasure(logk,m)
 end
 
 Base.:*(m::AbstractMeasure, k::Real) = k * m