Simplify implementation of Delta (#378)

* Simplify implementation of `Delta`

* Fix bug in `pairwise!` implementation

* Update Project.toml

Author: devmotion

Project.toml

@@ -1,6 +1,6 @@
 name = "KernelFunctions"
 uuid = "ec8451be-7e33-11e9-00cf-bbf324bd1392"
-version = "0.10.24"
+version = "0.10.25"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/distances/delta.jl

@@ -1,10 +1,18 @@
 # Delta is not following the PreMetric rules since d(x, x) == 1
 struct Delta <: Distances.UnionPreMetric end
 
-@inline Distances.eval_op(::Delta, a::Real, b::Real) = a == b
-@inline Distances.eval_reduce(::Delta, a, b) = a && b
-@inline Distances.eval_start(::Delta, a, b) = true
-@inline (dist::Delta)(a::AbstractArray, b::AbstractArray) = Distances._evaluate(dist, a, b)
-@inline (dist::Delta)(a::Number, b::Number) = a == b
+(dist::Delta)(a::Number, b::Number) = a == b
+Base.@propagate_inbounds function (dist::Delta)(
+    a::AbstractArray{<:Number}, b::AbstractArray{<:Number}
+)
+    @boundscheck if length(a) != length(b)
+        throw(
+            DimensionMismatch(
+                "first array has length $(length(a)) which does not match the length of the second, $(length(b)).",
+            ),
+        )
+    end
+    return a == b
+end
 
 Distances.result_type(::Delta, Ta::Type, Tb::Type) = Bool

src/distances/pairwise.jl

@@ -7,7 +7,7 @@ end
 pairwise(d::PreMetric, X::AbstractVector) = pairwise(d, X, X)
 
 function pairwise!(out::AbstractMatrix, d::PreMetric, X::AbstractVector, Y::AbstractVector)
-    return broadcast!(d, out, X, Y')
+    return broadcast!(d, out, X, permutedims(Y))
 end
 
 pairwise!(out::AbstractMatrix, d::PreMetric, X::AbstractVector) = pairwise!(out, d, X, X)