# Dict merge without promoting
**URL:** https://discourse.julialang.org/t/dict-merge-without-promoting/26648
**Category:** General Usage
**Tags:** type, dictionary
**Created:** [July 22, 2019, 8:23pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648 "2019-07-22T20:23:34Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@grahamas](https://discourse.julialang.org/u/grahamas)
#### Post date: [July 22, 2019, 8:23pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648/1 "2019-07-22T20:23:34Z")
Is there any existing way to merge without promotion? Maybe with constructing a dict that has union type? Right now I’m trying to merge dicts that may have values of Int or Float type, in an arbitrary order, and I need the values to retain their type. Is there a way to do this aside from simply writing my own method?
(also, is there a particular reason why merge works with promotion? For me at least it led to an error that was hard to track down, and seems somewhat surprising)
---
### Author:  [@sswatson](https://discourse.julialang.org/u/sswatson)
#### Post date: [July 22, 2019, 8:48pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648/2 "2019-07-22T20:48:06Z")
Yes, you can use a union type or just `Any`:
```julia
D = Dict{Int,Any}()
D[1] = 2
D[2] = 3.0
```
---
### Author:  [@Daniel\_Berge](https://discourse.julialang.org/u/Daniel_Berge)
#### Post date: [July 22, 2019, 9:08pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648/3 "2019-07-22T21:08:06Z")
If you need the key not to promote, you’ll need to use your own wrapper as far as I know. The key compares by `hash`, which per the docs says that
```julia
?hash
Compute an integer hash code such that isequal(x,y) implies hash(x)==hash(y). The optional second argument h is a
hash code to be mixed with the result.
```
---
### Author:  [@tkoolen](https://discourse.julialang.org/u/tkoolen)
#### Post date: [July 22, 2019, 10:17pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648/4 "2019-07-22T22:17:01Z")
You could create a `Dict` of whatever type you want and use `merge!`,
```julia
julia> d1 = Dict(1 => 2); d2 = Dict(2. => 3.); d3 = Dict{Union{Int, Float64}, Union{Int, Float64}}();
julia> merge!(d3, d1, d2)
Dict{Union{Float64, Int64},Union{Float64, Int64}} with 2 entries:
2.0 => 3.0
1 => 2
```
---
### Author:  [@Daniel\_Berge](https://discourse.julialang.org/u/Daniel_Berge)
#### Post date: [July 22, 2019, 11:52pm UTC](https://discourse.julialang.org/t/dict-merge-without-promoting/26648/5 "2019-07-22T23:52:24Z")
I misunderstood what was being asked, as I was thinking the question pertained to keys being promoted. So if it’s expected that `d[1.0] != d[1]`, you’d need a wrapper type.