`countmap` weird behaviour for -0.0

[jhbdiehl]

t = [0., -0.]
ct = countmap(t, [1 for e in t])

will output:

Dict{Float64, Int64} with 2 entries:
  0.0  => 1
  -0.0 => 1

Changing t to Integers

t = [0, -0]
ct = countmap(t, [1 for e in t])

or removing the weights

t = [0., -0.]
ct = countmap(t)

leads to the expected behaviour:

Dict{Float64, Int64} with 1 entry:
  0.0 => 2

Now all of this does not seem problematic until you start changing the keys, e.g.

Dict(keys(ct) .+ 1 .=> values(ct))

leads to

Dict{Float64, Int64} with 1 entry:
  1.0 => 1

in the first case, instead of

Dict{Float64, Int64} with 1 entry:
  1.0 => 2

Therefore I think this is not the intended behaviour. To be fair this could also be interpreted as a bug in the general Dict routine.