Fix countmap with -0.0 (#831)

Radix sort algorithm treated `-0.0` and `0.0` as equal, but
the dict algorithm treated them as different.

Author: nalimilan

src/counts.jl

@@ -356,7 +356,7 @@ function _addcounts_radix_sort_loop!(cm::Dict{T}, sx::AbstractVector{T}) where T
     # adding into the Dict
     @inbounds for i in start_i+1:lastindex(sx)
         sxi = sx[i]
-        if last_sx != sxi
+        if !isequal(last_sx, sxi)
             cm[last_sx] = get(cm, last_sx, 0) + i - start_i
             last_sx = sxi
             start_i = i

test/counts.jl

@@ -172,6 +172,14 @@ end
         @test cm_tx_missing == countmap(tx) == Dict(typemin(T) => 1, typemax(T) => 1, 8 => 2, 19 => 1)
         @test cm_tx_missing isa Dict{T, Int}
     end
+
+    # -0.0 and NaN
+    @test countmap([0.0, -0.0, 0.0, -0.0, -0.0], alg=:dict) ==
+        countmap([0.0, -0.0, 0.0, -0.0, -0.0], alg=:radixsort) ==
+        Dict(0.0 => 2, -0.0 => 3)
+    @test countmap([NaN, NaN], alg=:dict) ==
+        countmap([NaN, NaN], alg=:radixsort) ==
+        Dict(NaN => 2)
 end
 
 @testset "views" begin