# \`haskey\` and \`values()\` show different realities? \[SOLVED/CLOSED\]

**URL:** <https://discourse.julialang.org/t/haskey-and-values-show-different-realities-solved-closed/4907>\
**Category:** General Usage\
**Created:** [July 17, 2017, 6:04pm UTC](https://discourse.julialang.org/t/haskey-and-values-show-different-realities-solved-closed/4907 "2017-07-17T18:04:55Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [July 17, 2017, 6:04pm UTC](https://discourse.julialang.org/t/haskey-and-values-show-different-realities-solved-closed/4907/1 "2017-07-17T18:04:55Z")

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Here is a MWE:

```julia
D = 3; L = 2000
vectors = [rand(L) for i in 1:D]
d = Dict{Vector{Int}, Int}()
minima = [minimum(v) for v in vectors]
ind = zeros(Int, D)
ε = 0.001
for j in 1:length(vectors[1])
  for k in 1:D
    ind[k] = Int(ceil((vectors[k][j] - minima[k])/ε))
  end
  haskey(d, ind) || (d[ind] = 0)
  d[ind] += 1
  if d[ind] == 0
    error("For ind=$ind, the dict had 0!")
  end
end
#return [val/L for val in values(d)]
vals = values(d)
RL = length(vals)
ret = zeros(Float64, RL)
i = 1
for val in vals
  val == 0 && error("val was 0")
  (x = val/L; x == 0) && error("val/L was 0")
  ret[i] = x
  i += 1
end

```

Running this code gives you error “val was 0”.  
So what is happening here is that I get a dictionary with some of its values are 0. However, this cannot be correct, because the dictionary values are set with the lines:

```julia
haskey(d, ind) || (d[ind] = 0)
d[ind] += 1

```

therefore, if a key exists, its value _must be at least_ 1.

What is happening here?

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<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [July 17, 2017, 6:11pm UTC](https://discourse.julialang.org/t/haskey-and-values-show-different-realities-solved-closed/4907/2 "2017-07-17T18:11:04Z")

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Solved…?

I have seen by examining `keys(d)` that all the keys are the same… Clearly one cannot use Arrays for keys of a dictionary (or at least not mutate them).

By using `ind = @SVector [Int(ceil((vectors[k][j] - minima[k])/ε)) for k in 1:D]` instead, it works.

EDIT: If you run the above example with very low `ε` you get all the values to be 1 (this happens by chance, because probably the random numbers are well spread out).

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [July 17, 2017, 6:26pm UTC](https://discourse.julialang.org/t/haskey-and-values-show-different-realities-solved-closed/4907/3 "2017-07-17T18:26:41Z")

</div>

You can’t modify keys for a `Dict`.

On the one hand, this is perfectly obvious to everyone with a minimal exposure to basic data structures (it is a hash table), on the other hand, this comes up all the time, so perhaps a remark about it would be in order somewhere in the manual, or the docstring of `Dict`.